US 2502881 A
Description (OCR text may contain errors)
PII 4 1950 E. w. PARKER 2,502,881
HOUSEHOLD CLEANING COMPOSITION Filed 0013. 17, 1945 Patented Apr. 4, 1950 UNITED STATES PATENT OFFICE HOUSEHOLD CLEANING COMPOSITION Elizabeth Weston Parker, Washington, D. C.
Application October 17, 1945, Serial No. 622,820
Claims. l This invention relates to household cleaning compositions; and it comprises alkaline cleaners of the type used in the household for cleaning Windows, painted Work, iioors, tiling, wood-work,
-` glassware and the like; said cleaner being a nely divided mixture of alkaline detergent salts, such as hydrated sodium metasilicate, ammonium phosphate, sodium pyrophosphate, diand tri-- sodium phosphate, sodium borate, sodium carbonate and the like, and having incorporated therein a small quantity of at least one pl-I indicator having the characteristic property of changing color Within a pH range of about 7.5 to 9.7 to give a warning dominant color at least at the higher pH values; said mixture also advantageously including a soap powder and/or a wetting agent; all as more fully hereinafter set forth and as claimed.
Household cleaners of the type used in general cleaning Work about the house are in widespread use. These cleaners contain at least one buffering inorganic detergent salt and may contain in addition soap and/or wetting agents or the like. When added to a soft Water in cleaning concentrations, which usually range from about 1A, to 3 teaspoonsful (i to 1/2 ounce) to the quart or about 0.15 to 2 per cent by weight, they produce a pH above 8.3. The pH produced at these concentrations should not substantially exceed 10.5 and preferably not 9.5, in order that the cleaning solutions thus formed can be applied with the hands without damage either to the work or to the hands. The maximum pH produced at concentrations of 5-10 per cent of cleaner should not be above about 11. In other words these cleaners are slightly more caustic than pure soaps but less caustic than industrial cleaners, the pH of Whose solutions frequently exceed 12. This latter type of cleaner cannot be applied by hand.
While household cleaning compositions are usually fairly well buffered, so that their pH changes only slowly With concentration, it is generally true that, if used in concentrations much above the minimum recommended, these cleaners are likely to be deleterious or irritating to the skin. For economy reasons, as Well as for best results, it is also desirable that these compositions be used in solutions close to the minimum required for production of the desired cleaning effect.
The packages in which these cleaners are sold invariably give directions to prepare the desired cleaning solutions .by adding so many teaspoonfuls or so many ounces oi the cleaner to a quart or a gallon of Water or the like. Directions of this type, of course, leave much to be desired. The persons using these cleaners must of necessity employ ordinary tap Water in making the cleaning solutions and tap Waters vary widely in hardness. Directions which would be suitable for the Water in one city might be quite unsuitable lor the Water in a neighboring city.
Attempts have been made to overcome the above difculties by the use of simple dyes added to cleaning compositions. The dyes used in this manner did not change in color upon change in pH but an attempt was made to add them in such quantities that, when the proper amount of composition was added to the Water, a deiinite fluorescent or colored'effect was produced. It is obvious, of course, that the color produced by such a method depends only upon the amount of dye added to the Water, regardless of the hardness of the latter. If the dye is evenly dispersed through the cleaner, the color of the cleaning solution increases directly as its concentration increases. There is no sharp change in color and there is no way of judging by the inexperienced what depth of color is correct or how Soft a water is produced. The dye, therefore, serves no useful purpose until the user of the composition has had considerable experience in making up cleaning solutions from a single tap water.
My invention is applicable to cleaning compositions of widely dilerent character. Any of the usual alkaline detergent salts can be employed in these compositions, including sodium silicates, sodium phosphates, sodium car-bonates, ammonium salts, sodium borates, salts of quaternary ammonium bases, the so-called cationic soaps and the like. It is only necessary that the composition be one which when added to Water produces a change in pH over a range which extends throughout and somewhat beyond its optimum concentration range. The pH indicator for a given cleaning composition must be selected, of course, in such manner as to produce a characteristic color at at least some point Within the optimum concentration range of the cleaner.
I have found that When a critical quantity of certain pI-I indicators are admixed with dry household detergent compositions and when these dry mixtures are added to water gradually, a color change Will become noticeable when optimum cleaning concentrations are reached, such as one spoonful to the quart, for example, and that when more cleaner is added the color changes rapidly in intensity, not directly with the quantity added, as in the case of an ordinary dye, but more nearly as the square of the quantity added. The
low a pH of 9.7.
reason for this is that the color change is due not only to the increased concentration of the dye in the water but also to the pH of the solution. The total color change due to these faotors can be made very marked by suitable choice of indicator and detergent composition. Owing to the rapidity of color change produced in this fashion, a person, told to add cleaner to water until a faint color is produced, might stop when he had added an excess amounting to say 25 to 50 per cent but wouldrarely exceed the latter figure, especially if the directions should state that additional water should be added if a distinct color should develop. This new process therefore provides a method of preparing cleaning solutions which takes into. account the hardness of the water.
When the pH of the water rises, 'due to addition of cleaner, to about 8.2 this provcsthat the bicarbonate or temporary hardness of the water has been neutralized by the alkali of the cleaner. Usually a slight excess of` cleaner above this point produces satisfactory cleaning without beingk irritating to the hands.
A cleaner which does not produce an eiective .cleaning solution at a pH below about 9.7 cannot be classed as a `household cleaner. It follows that a suitable pH indicatoivfor the purposes of this inventionmust have a color range the lower end of which extends at leastsome distance be- And, as will beshown later,.for best results, the lower end of the range of the indicators dominant Vcolor should not lie below a pH of about 7.2.to 8.0.
I have found surprisingly that for best results the pI-I indicator `shouldbe chosen in such :fashion that it produces a change in color as close as possible to the pI-I at which the cleaning cornposition `first becomes effective. In other words for best results the end point of the indicator should occur at a pH substantially coinciding with that of the lower end of the veffective cleaning range of the detergent. Thus, if the composition rstmakes an eiective cleaning solution upon the addition oabout arteaspoonful `to a quart of soft water andif a pH of about-8.7 is produced at thisconcentration, for best results an indicator shouldibe chosen .whose colorrange starts, i. e. whose end pointflies eter-just below apI-I of 8.7, say from about 8.3 to 8.7. .If the end point lies below about 7.5,the color change produced per unit of cleaneradded in-the eiective cleaning range will be noticeably inferior and will approximate that produced by a simple dye.
The explanation for theserunexpected results is believed to lie in the accompanying drawing which shows curves of color .intensity for two different indicators as a function of the amount of detergent added to water-to produce a cleaning solution.
In this figure a curve (marked pI-I Curve) is given which shows the pH values of the solution as the cleaning composition is added thereto. The cleaner illustrated is a typical household cleaner having an optimum cleaning range of from 0.5 to 0.75 per cent dry weight giving a pH ranging from about V8.7 to 9.2. The concentrations are plotted as abscissas with the pHvalues as ordinates, the numerical values of thepI-I being givenalong the axis at the left of t-e figure. This curves starts at apHlof 7 with zero concentration of detergent. The pI-I-increases rapidly with small increases of `concentration at the start of the curve but the rate of increase rapidly falls o until, -at a concentration of about 2.5
4 per cent detergent the curve rises above a pH of 10 but becomes almost parallel with the concentration axis due to the buering eiect of the detergent salts.
A line representing the color intensity of a simple dye in the solution is also given. rIhis is, of course, a straight line since the dye is evenly dispersed throughout the cleaner and its color intensity in the solution increases directly with the concentration of the detergent salts. It is assumed'that the dye used does not change color with pI-I and that when the lino representing its concentration crosses the minimum effective cleaning-concentration, that is, 0.5 per cent, its color rst becomes definitely detectible, as would vbe thezcase if such a dye were to bc employed in a detergentto indicate optimum concentrations of detergent. The color intensities are indicated on the axis at the right side of the gure and are expressed in arbitrary units. It is assumed that color perception occurs at a dye concentration of 1.5 of these units. The line representing the color intensities of a simple dye thus is a straight line starting at zero and passing through `the point representing a 0.5 per cent.
concentration of detergent-'and a color intensity of 1.5 units. The lower dotted section of the line indicates the region in which a colored dyc is present, itscolor being imperceptible in practice owing to its low concentration.
Thecurve marked Color Intensity, Indicator A isdravvn upon the assumptionzthat a dye is employed which starts .to cha-nge in color at a pH ofI about 8.6. The minimum effective concentration of detergent isassumed as before to be 0.5 per cent by'weight at which. point the pH of the solution, as read from the pH curve, is about 8.7. In other words, using this indicator, the quantity of indicator which should be added to the detergent salts is that required to produce a detectable color when the pH reaches a Value of 8.7, corresponding to a detergent concentration `of 0.5 per cent. .The curve representing colorintensity obviouslystartsat a concentration corresponding to a pHof about-8.6, at which the detergent concentration is about 0.35 per cent. The curve also must pass through the point of color perception (1.5 color intensity units) and at a concentration of 0.5 per cent detergent. The colorintensity curve for the indicatorin question rises rapidly at the start, eventually becoming substantially parallel to the color intensity curve for the simple dye as the change in pH upon the additionof detergent approaches zero. Here againthe lower section of the curve represents the condition wherein a color is actually present but practically imperceptible owing to lack of dye concentration. It will be noted, however, that this color intensity curve crosses the axis representing zero color intensity at a point corresponding to a concentration of detergent of about 0.35perrcent, i. e. a pH of 8.5. It is .obvious therefore that, if a detergent concentration of 0.5 yper cent is operative, a concentration.of 0.35 per cent wouldbesubstantially equally effective, the differencebeing Very small.
Itis thus evident that no harm would result in adding a considerablefexcess of this particular indicator A tothe dry detergent since, even ii its color became detectible at a pI-l' of 8.6-the extreme lower end ofthe .coloi` range-a rather satisfactory .detergent solution would be produced at this pH. This. shows that, the closer the lower end ofthe color-range of the indicator to the pH corresponding to the optimum cleaning concentration of the detergent, the less the accuracy required in -adding the indicator to the detergent. Of course, for economy reasons, it is desirable to add only enough indicator to produce a definite color perception at a point corresponding to the optimum cleaning concentration. But the increased flexibility obtained and the lower accuracy required, from the use of an indi cator whose change point is close to the optimum pH of the cleaner, are highly important. It is evident, of course, that it would be possible and most advantageous to employ an indicator the lower end of whose color range coincided with the pH of the optimum cleaning concentration, pro vided that such an indicator should be available.
The curve marked Color Intensity, Indicator B in the drawing represents the results obtained using an indicator the lower end of whose color range lies at a pH of about 8.1. This curve also passes through the color perception point at 1.5 color intensity units and a concentration of 0.5 per cent. It lwill be noted immediately that this indicator is not as effective as indicator A in designating optimum cleaning concentrations. Thus, indicator A produces a color intensity of about 3.2 units as the concentration changes from 0.5 to 1 per cent, while the indicator B gives a similar color intensity change of only 2.4 units. This compares with a color intensity change for the simple dye of 1.6 units. Indicator A is about twice as eiectiv-e as the simple dye while indicator B is about half again as eiective.
It is evident from the above that the usefulness of an indicator rapidly falls o as the lower end of its dominant color range approaches a pH of 7. In fact it is evident from the drawing that an indicator the lower end of whose color range approaches 7 would have no advantages over a simple dye in indicating optimum cleaning concentrations. Practically speaking, an indicator the lower end of whose color range is below 7.2 is not advantageous in the present invention.
My tests with indicators conirm the conclusions drawn from the curves of the drawing. A simple test can be made to determine what proportion of the color change produced by a given indicator in one of my detergent compositions is due to pH change. In this test three quart bottles are filled with water and to each is added a suflicient amount of indicator to produce a perceptible color when the detergent (free from indicator) is added thereto in optimum cleaning concentration, say l teaspoonful, the amount of indicator added to each bottle being the same. Then to one of the bottles a teaspoonful of detergent (free from indicator) is added, to the second one-half teaspoonful and to the third one-fourth teaspoonful. If there is a denite color difference between bottles 1 and 3 or l and 2, it follows that the indicator in question is suitable for use in my invention, since it produced a change in color which is more than that produced by-mere change in concentration of indicator. In the same test three other quart bottles can be filled with water and to these bottles may be added l, 1/2. A spoonful, respectively, of the same detergent with indicator admixed. It will, of course, be noted that the color differences in this second series of bottles is much more marked than in the rst set since, to the color change produced by change in pH, there is added the color change due to concentration of the indicator.
If phenolphthalein is used in the above test, having a color range or end point ending at about 8.1-8.3, it will be noted that in the rst series of` bottles the color difference between bottles 1 and 3 will be rather small, showing that the end point this indicator, corresponding approximately to Indicator B of the drawing, falls close to the lower end of the useful cleaning range. The second series of bottles will show denite color differences due, of course, primarily to the concentration effect. In comparison, the indicator phthalein red shows a deiinite color diierence between all the bottles of the first series and an even greater diierence between the bottles of the second series, the latter being the sum of the color differences due to pH and to dye concentration.
The curves in the drawing do not tell the complete story for the reason that it is recognized that the maximum rate of detectible color increase n a pH indicator lies on the side of its lower or less dominant color, and usually close to the end of its color range. I have found that it is not practical to employ an indicator whose color disappears or becomes less dominant at the optimum pH of the detergent when approached from the low side. It follows that for best results the pH produced at the optimum cleaning concentration of the cleaner should lie not only within the color range of the indicator but also between the half-transformation point and the lower end of the color range of the indicator. It is also evident that the curves of the drawing do not tell the complete story for the reason that the indicators thymol blue and meta cresol purple when subjected to the above tests, seem to produce at least as good results as phenolphthalein in spite of the fact that the lower ends of their color ranges are usually stated as lying at a pH of 8.6 and 7.6, respectively. A possible explanation for this may be that the col-or changes produced in the latter indicators, due to pH, may be greater than in the case of phenolphthalein through the range of optimum cleaning concentrations. That is, the bulk of the color change in the case of phenolphthalein may occur close to its lower end point. The primary requirement is that the indicator produce an appreciable color change due to pH within the optimum cleaning concentration rang-e of the detergent.
It is possible with the aid of the facts brought out above to formulate rather denite specifications for the indicators which are useful in this invention. These indicators must change in color or intensity, that is, give a color change throughout the pH range corresponding to the optimum cleaning concentrations of the detergent. This color change must be a change oi the dominant color of the indicator and this change must terminate at its lower end at a pH ranging from about 7.2 to the pH corresonding to the optimum cleaning concentration of the detergent. And for best results the indicator should be one whose half transformation point lies at or above the pH corresponding to the optimum cleaning concentration of the indicator.
I have further found it advantageous to incorporate at least some soap, that is, an alkali metal salt of a high molecular fatty acid, in my detergent composition. The soap produces a slightly milky or opalescent effect which tends to enhance the color produced by the indicator. It furnishes a white background, so to speak, against which the color may be viewed, even' when the solution is made up in a pail, for example. The quantity of soap added for this purpose should be at least about 25 per cent vby weight of the detergent.
My invention also includes a method of making the :described detergent compositions. I have found that the :best .wayqoi -adding .color indicators .to a;detergent.composition isby spraying anvaqueous orfalcoholicosolution oflthe indicator on a 'mass Otdetergentlwhile .the ymass is being agitated. When .the.indicatorrsolution dries the detergent particleszare .thenvuniforimly coated with the dried=residues of `the solution and segregation is avoided. If the detergentis not thoroughly dry it will ;,become .imoist rand somewhat sticky. during this:operation. And;the indicator usually changes ,to-its colorzin alkaline solution, that is, phenolphthalein, for example, produces a pink color. Thissame `colorchange will occur if the detergent is dehydrated prior to the mixing,T operation :provided that it is heatedltoo strongly duringthei mixing. I have found that compositions.; made up in-these ways tend to change'ln color upon. standingina relatively dry atmosphere; producinga iinalacolor corresponding to the neutralcolor of the indicator. That is, a detergent containing phenolphthalein will eventually become v.almost `colorless, a detergentfcontaining phthalein red will become yellow, a detergent containing thymol blue will become adightyellowto orange-color and a detergent `containing .meta cresol purple will vbecome a light brown color. The :stable colors of these detergentsapparently.correspond tothe neutral colors of the indicators.
t is, oi4 coursegdisadvantageous to haven` detei-gent change in color during storage and I have. found a method of avoiding'this difficulty. In this method the v,detergent is dehydrated at least partly beiorethe mixing of the color.in dicator is completed. Preferably the detergent is thoroughly dehydrated before the mixing operation. The mixing operation is then conducted at a temperature ranging from about to 60 C., thetemperature.employed depending upon theindicator but being so chosen that the indicator does .not change substantially in color upon contact with the detergent. When meta cresol'purpleis employed the dehydrated detergent should be kept atiroom temperature or below during the mixing .operationtwhile with phthalein red the temperature may approach 60 C. It is advisable to use .alrather concentrated solution of the indicator so that not too much solvent will be added to the detergent. Further dehydration after the addition of the indicator can thus be avoided. :This method produces a stable color.at once=which color .will not change unless the detergent is hygroscopic.
It is usually advantageous to employ a compatible wetting agent in my-.cleaning ccmpositions. This wetting agent can `be -made to lperform a double function, that is, awettingfagent can Abe employed 4which will serve as a .vehicle for the pH indicator as well as a .wettingagent per se. A large number of wetting agents are available which are of oily character and'which readily dissolve pH indicators. These wetting agents can be distributed .over the'surfacesof the cleaner particles andtendto prevent'caking. They also prevent directcontactof theindicator with the alkaline salts .of .the cleaner, which'may be important if the indicator isnothighly-stable towards alkalis. Among the wetting agents which are suitable for'use withfmostalkaline detergent compositions, there may be mentioned triethanol amine, pine oil, secondary alcohol sulates, such as Tergitol 4 or .'l'iergitolx'lfpolymerized sodium salts of alkylated naphthalene sulionic acids, monoethylphenol .sodum-rmonosulfonate, vsulfonated :castor `oil,su1fonated cresylicbase compound and sulfonated `cetyl alcohol.
It is usually advantageous to dissolve or disperse. the pH indicator in the wetting agent before mixing -theztwo with the detergentsalts. If the .wetting agent is a solid, it can be melted or .preferably an inert solvent-is used to maken solution of indicator vand wetting` agent. In the nal mixing operation, wherein the solution or dispersionofthelindicator in the wetting agent i: mixed-With the detergent salts, it is desirable to spray the.y solution or dispersion over the salts whilethe latter arebeing agitated. This procedure evenly distributes both wetting agent and indicator throughout the mass. The indicatorwettingagent combination forms a lm coating on'the salts and helps to prevent caking, for example. Any of `the usual Iorganic solvents which are inerttowards Athe wetting agentand the indicator can be used, such as alcohols. ketones or ethers. Usually either ethyl or propyl alcohol will be found suitable.
Both thepI-I indicators and the wetting agents can be utilizedv in my compositions in small proportions. The wetting agent can bey used in proportions ranging from about 0.2 to 10 per cent by weight while the concentration of the indicator may range from about 0.004 to 0.02.per cent, depending upon the indicator. With some indicators it is possible to employ upto 1 per cent by weight. For .reasons 4of economy it is preferred to employ the minimum concentrations of indicator which are compatible with .the desired results and these concentrations usually range from about 0.004 to 0.01 per cent.
Myinvention may be illustrated by reference to the following specific examples which represent practical operating embodiments thereof.
Example 1 A composition was compounded containing the following:
Parts Sodium soap 75 Sodium metaborate tetrahydrate 12.5 Tetraesodium pyrophosphate (10H20) 12.5
This mixture was ldehydrated by heating to about 60C. while stirring and then cooled to approximately room temperature. An aqueous solution'ofphenolphthalein (about 0.04 per cent by weight) was then'sprayed on the mixture while stirring and spraying was continued until a teaspoonful of the mixture, when added to a quart of water, produced a detectible pink color. The water in the phenolphthalein solution was rapidly absorbed by the detergent, the latter retaining its dry pulverulent consistency. The color of the mixture was only slightly off white and this color Wasfound to be stable uponstanding. From the concentration of the phenolphthalein solution and the quantity added it was estimated that 0.004 per oentphenolphthalein on the dry basis had'been added.
Example 2 A. composition was compounded containing the following:
Parts Sodium soap 50 Sodium ,carbonate (10H20) 15 Di-sodium phosphate (12H20) 15 Sodium metasilicatepentahydrate 20 This-icomposition wasdehydrated and then an alcoholic solution of thymol blue wasaddeddropwise while stirring, the composition being slightly above room temperature. This was continued until the detergent produced a light blue color when added to water in the amount of one spoonful to a quart. The thymol blue added amounted to 0.01 per cent on the dry basis. The nal composition was a light yellow color.
Example 3 The composition of Example 2 was dehydrated as before and then cooled to a temperature of about 15 C. when an alcoholic solution of meta cresol purple was sprayed on while stirring. This solution had been acidied slightly by the addition of acetic acid to produce a yellowish brown color. The addition of meta cresol purple was continued until the composition, when added to water in the amount of 1 teaspoonful to 1 quart, produced a light purple color. This required a total of 0.008 per cent on the dry basis. The color oi the resulting mixture was a light brown which faded only slightly upon standing.
It was found that, if the detergent salts were heated to a temperature of about 70 C. during mixing, a light blue to lavender color resulted, which color faded to a light brown upon standing.
Example 4 A composition was compounded containing the following components:
To the above mixture, after dehydration, an alcoholic solution of phthalein red was added while stirring until a light pink color was produced upon adding 1 teaspoonful of the mixture to 1 quart of water, the quantity added being about 0.014 per cent on the dry basis. The mixture was maintained at a temperature of about 40 C. during the mixing and the resulting color was found to be yellow. If slightly overheated this mixture produces a pink composition whose color gradually changes to yellow on standing. A concentration of phthalein red ranging from about 0.007 to 0.015 per cent is satisfactory for producing other detergent compositions within this invention.
Example 5 The composition of Example 1 was dehydrated and to this was added an alcoholic solution of a l Example 6 Parts Tetra-sodium pyrophosphate (10H20) 78 Sodium carbonate (10H20) 26% Pine oil 3 Nile blue 1/ This indicator when added to tap water of about average hardness in the amount of about 1 teal 0 spoonful to the gallon produces a reddish mauve to rose color, a concentration which will be found suitable for most work, at lower concentrations a blue color is produced.
Example 7 Parts Trisodium phosphate (12H20) 60 Sodium sesquisilicate (11H20) 27 Daxad l1 21/2 m-Nitro phenol 1,/2
This composition when added to water produces a faint yellow color when the concentration is about right for light cleaning and a bright yellow when it is suitable for heavier work.
Example 8 Parts Soap powder 20 Sodium metasilicate ennahydrate 43 Sodium metaborate tetrahydrate 30 Beaconol A 5 Thymol blue 0.02
This composition makes a useful household cleaner and produces a yellow color at concentrations too low to be effective, a green color over a range suitable for light work and a bluish green to blue color at concentrations suitable for ordinary work.
While I have described what I yconsider to be the most advantageous embodiments of this invention it is evident that various modications can be made in the specific compositions and mixing procedures set forth without departing from the purview of this invention. As pointed out previously the alkaline detergent salts employed in my compositions can be widely varied in nature and proportions depending upon the particular work to be done. For some types of work a rather high proportion of wetting agent is called for. But for ordinary purposes both the dye and wetting agent are employed in small amounts as compared with the detergent salts. Any suitable mixing method may be employed to compound my compositions. It is always desirable to select alkaline salts for my cleaner which are stable and non-hydrogroscopic in spite of the fact that the wetting agent tends to prevent caking.
When wetting agents are employed in rather high proportions, it is possible to tint the dry composition a color which corresponds to that produced upon dissolving the composition in water at the best cleaning concentration. This is accomplished by treating the indicator with a small amount of a slightly alkaline buffer solution of the desired pH, just prior to dissolving or dispersing it in the wetting agent. After the mixture is coated on the cleaner particles, the color then remains reasonably stable. It is more advantageous to buffer the wetting agent-indicator mixture to stabilize the color. One of the most convenient buffers to employ for this purpose is borax with a small amount of boric acid or primary sodium phosphate added. But other compatible buffers can be used. With cleaning preparations prepared in this manner the user can be told merely to match the color of the cleaner in making the cleaning solutions.
In the case of most cleaning compositions it is possible to so select the color indicators that three colors are produced upon adding the composition to water in different proportions. In this case one color may indicate when the concentration of the indicator is too low, another when it ls satisfactory for ordinary cleaning and the third color may be used asi av Warningthat the-concentration is-too high or at least so high that'thesolution should not be used onpaints,I for-example; A mixture of acyl red and thymol phthalein or 1,2,3-xylenol phthalein, for example, is red up to a pH of about 9.5 when it begins to turn a mauve color and at a pH of vabout A10.5 itbecomes a'bluish green. The indicator alkanin turnsfrozn red, through mauve to blue in the range of 8.3*to and thus it alone forms a goodthree color; indicator. A mixtureof alpha naphtholA benzein and nitrothymol sulfonphthalein is violet up to a pH of about 9.2 when it begins` to turn a brownish color and then at a pH of about 10.5 itturns green. It should be noted that, when three-color indicators are used as described, the pH is indicated notA only by the color intensity but also by the shade of the color itself. This increases theaccuracy of this method. Other modifications of my. invention whichiallwithin thescope ofthe following claims will be immediatelyv evident to those skilled in this art.
This is a continuation-in-part of my copending application, Serial No. 569,625, led December 23, 1944, now abandoned.
What I claim is:
1. A detergent composition suitable for use in householdcleaning which comprises a mixture of nely-divided, solid, inorganic, alkaline detergent salts which, when-dissolved in water in the concentration range of about 0.15 to 2 per cent by weight, produce cleaning solutions which have pI-Ifvalues Within the range ofabout 8.3 to 10.5
and producing pI-I'valuesnot` substantially ex- I ceeding 11 when added to water in concentrations up to about 10 per cent by-weight, said `composition also containing at least abouti 25per centby weight of soap and from about 01.004 to0.02 per cent of a pH indicator having theproperty of changing in color due to -pI-I within said range of 8.3 to 10.5 and-Whose end point occurs-at a pH substantially coinciding with the pH corresponding to the lower end of the effective cleaning range of `said detergent composition, the quantity of indicator present being capableof producing a detectible coloration only upontheaddition of sufcient detergent to water to produce approximately optimum cleaning concentrations; said coloration then increasing in intensity upon iurther addition of the detergent due both to in'- crease in indicator concentration and to `change in pH.
2'. A detergent composition suitable for use in household cleaning which comprises a mixture of finely divided, solid, alkaline-reacting.` detergent salts capable ofbuffering solutions of said composition so thatthe pH values of said solutions do not substantially exceed 11`at concentrations of up to about-10 percent by weight, said composition forming cleaning solutions when added to water-in quantity producing concentrations within the range of 0.15 to 2 per cent by weight with corresponding pH' Values 1 within the range oi-about-B 4to 10.5, said composition also containing from about' 0.004 -to 0.02 perifcent by weight of at least one pH' indicator:4 having? the property cf producing a1 characteristic change; in color within the range-of pli-corresponding` to the optimum cleaning concentrations-of said detergent,- the'lower end-of the dominant color range of said-z indicato-rwsubstantially: coinciding with .the pH` corresponding to the lower end of the Veiective cleaning range of said composition, the quantity of pH. indicator presentbeingsuicentto produce a detectible coloration only: when sumcent detergent is dissolved-in water to give a solution within the cleaning range of frOm about 0.15 -to 2.0 vper cent byweight; said detergent upon gradual addition to Water initially producing'- a detectible color withinsaid cleaning range, said color then increasing in intensity upon further addition of the detergent due both to increase in indicator concentration and to change in pH.
3. A dry nely-divided detergent composition comprisingapluralityof alkaline detergent salts producing-a buiering eiect upon aqueous solutions and a pH within the range of about 8.3 to 9.7 at-concentrations within the range of about 0.15 to 2 per cent by weight with a maximum pH of not substantially above l1 at concentrations of up toabout l0 per cent, said composition includingr at least about 25 per cent of a soap and from about 0.007v to 0.015 per cent by weight of phthalein redsulicient in amount to produce a detectible color onlywhen sufficient detergent is dissolved in water to give a cleaning solution within. the cleaning range of about 0.15A to 2.0.per cent by weight; said detergent upon gradual .addition to water initially producing a detectible color within said-cleaning range, said color thenincreasing in intensity upon further addition of the detergent due both to increase in indicator concentration and to change in pH.
4, A finely-divided, solid; householdv detergent composition comprising a mixture of detergent saltswhich, when. dissolved in water at a concentration ranging fromaboutl 0.15 to 2.0 per cent by weight, producesa cleaning solution having a pI-Iwithin'the range'of fromv about'8.3 to 10.5"J the solid particles of said composition being uniformly coated with-the dried, residues of a solution in a volatile solvent ofa pH indicator capable of changing color1 withinY said pH range, the lower end 4of the. color range otsaid indicator occurring at a., pH substantially coinciding with that ofthe lower end of. theeiective cleaning range of thecompcsition, the quantity of pI-I indicator present in the composition being within the range of from about 0.004 to` 0.02per cent by weight and sumcient .to produce a detectible coloration when said composition is dissolved in water to give a cleaning solution having aconcentration within said range.
5. The process of making a detergent composition the color of whose solutions is sensitive to change of pH Which comprises dehydrating a solid detergent composition comprising a plurality of alkaline detergent salts capable of buffering aqueous solutions of said detergent so that at concentrations of from about 5 to 10` per cent the maximum pH produced is not substantially above 11; the composition having the property, when dissolved in water in the amount of from about 0.15 to 2 per cent by Weight, of producing cleaning solutions within'the pH range of from about 8.3 to 10.5; gradually adding to the said composition a solutionin a volatilefsolvent of apH indicator having the property of changing in color due to changein pH within the; pH range of 8.3 tc:.l0.5; said indicator .being'added in quantity amounting to from about 0.004 to 0.02 per cent by weight on the dry basis; and while agitating and maintaining the temperature below about 60 C., whereby a composition is produced whose color isstable and corresponds'to'the natural color of said indicator.
ELIZABETH WESTON PARKER.
(References on following page) 13 14 REFERENCES CITED Number Name Date The following references are of record in the 213651215 Rhodes Dec- 19 1944 le 0f this patent: FOREIGN PA'IENTS UNITED STATES PATENTS 5 Number Country Date Number Name Date 488,648 Great Brltain July 11, 1938 1,721,809 Buchanan July 23, 1929 OTHER REFERENCES al'lvll g Modern pH and Chlorine Control, booklet of W. 178;735 Behrman NW .7 1939 lo A. Taylor and Company, Balt. 1943) 6th ed.,
- a es 40 and 48. 2,137,536 Avedikian Jan. 16, 1940 p g