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Publication numberUS2829107 A
Publication typeGrant
Publication dateApr 1, 1958
Filing dateJul 28, 1955
Priority dateJul 28, 1955
Publication numberUS 2829107 A, US 2829107A, US-A-2829107, US2829107 A, US2829107A
InventorsRuff Edgar E, Smith Elwin E
Original AssigneeLever Brothers Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Nontarnishing cleaning compositions containing ferrous salts
US 2829107 A
Abstract  available in
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Description  (OCR text may contain errors)

United States Patent NONTARNISHING CLEANING COMPOSITIONS CONTAINING FERROUS SALTS Edgar E. Ruff, Bergenfield, and Elwin E. Smith, Paramus, N. J., assignors to Lever Brothers Company, New York, N. Y., a corporation of Maine No Drawing. Application July 28, 1955 Serial No. 525,065

12 Claims. (Cl. 252-137) This invention relates to cleaning compositions containing tarnish inhibitors and more particularly to polyphosphate compositions containing ferrous salts as tarnish inhibitors.

Compositions containing polyphosphates are now widely used for detergent and other purposes. Aqueous solutions of polyphosphates tend when at certain pH values to tarnish German silver (a nickel-zinc-copper alloy) to a variety of shades from yellow to bluish-black, especially if the solutions are at elevated temperatures and are allowed to remain in contact with the metal for several minutes. Since German silver is frequently used for household articles commonly washed in polyphosphatebuilt detergent compositions, it is evident that this is a serious problem.

In accordance with the instant invention heat-dried polyphasphate compositions are provided containing a tarnish inhibitor which composition will minimize the formation of tarnish upon German silver. The tarnish inhibitors of the invention are water-soluble inorganic and organic ferrous salts, for example, ferrous acetate, ferrous ammonium sulfate, ferrous bromide, ferrous chloride, ferrous chloroplatinate, ferrous iodide, ferrous lactate, ferrous nitrate, ferrous perchlorate, ferrous potassium oxalate, ferrous sulfate, ferrous thiocyanate, and ferrous thiosulfate.

An amount of the water-soluble ferrous salt would be added to the polyphosphate composition suflicient to give tarnish inhibition when the composition is used in a normal way. It will be understood that the amount required will depend in part upon the tarnish-inhibiting properties of the particular ferrous salt in question, upon the tendency of the polyphosphate with which it is used to tarnish German silver, upon the amount and nature of the polyphosphate present, and upon the presence of components which may enhance the tarnish inhibiting effect of the ferrous salt, e. g., silicates or organic non-soap detergents. It was found that the minimum amount of ferrous salt necessary to impart adequate protection against the formation of tarnish is in the range from about 1.5% to about 6.5% of the ferrous salt based on the weight of polyphosphate. The maximum amount of the ferrous salt is not critical, but more than is necessary to give the desired effect usually would not be used, and of course an amount in excess of that soluble in the solution would not be used. In most cases, the maximum suggested would be about 7% based on the weight of polyphosphate.

The ferrous salts of the invention are effective as tarnish inhibitors in both hard and soft water.

The tarnish inhibitors of the invention are effective with water-soluble alkali metal polyphosphates at pH values where such polyphosphates tend to tarnish German silver, i. e., within the range of about pH 7 to about pH 10 and 2,829,107 Patented Apr. 1, 1958 particularly in the pH range of 9.5 to 9.9. Typical examples of suitable alkali metal polyphosphates include pentasodium and pentapotassium tripolyphosphates, tetrasodium and tetrapotassium pyrophosphates, sodium and potassium hexametaphosphates, and hexasodium and hexapotassium tetrapolyphosphates. The amount of the alkali metal polyphosphate present in the composition is not critical since the composition may consist of an alkali metal polyphosphate and a water-soluble ferrous salt, the amount of the ferrous salt being based upon the weight of the polyphosphate.

A peculiarity was noted in that the tarnish inhibitors were ineffective against a tripolyphosphate alone but they were effective when the tripolyph-osphate was used in conjunction with an organic non-soap detergent or an organic non-soap detergent and a silicate.

The heat-dried polyphosphate detergent compositions containing a water-soluble ferrous salt may optionally contain an organic non-soap detergent as well as small amounts of supplemental builders. The tarnish inhibitors display enhanced tarnish-inhibiting action in the presence of theorganic non-soap detergents as well as in the presence of silicate builders. Such compositions contain conventional proportions by weight of an organic non-soap detergent, usually within the range between 5% and 40%; an alkali metal polyphosphate in an amount, usually between 5% and 50%; a water-soluble ferrous salt in an amount to lessen the tarnishing action of the polyphosphate, and the balance supplemental builders and inert materials.

The organic non-soap detergents may be either anionic, cationic, or nonionic detergents.

The alkylaryl sulfonates are a class of detergents well known in the art under this name. One example thereof are the sulfonated phenylpolypropylene alkanes, characterized by the branched chain structure of polypropylene and a tertiary alkyl carbon at the benzene ring, and having the following general structure:

. SOsM where M is hydrogen, an alkali metal or an organic amine cation, and R and R are alkyl, of the type formula C H and at least one R is a polypropylene group, the whole alkyl group containing preferably 12 to 15 carbon atoms. These are known compounds, whose preparation and properties are set forth in U. S. Patent No. 2,477,383 to Lewis, issued July 26, 1949; they are available in commerce under the trade names Oronite, Ultrawet, and Neolene.

Another class of useful detergents are the amidoalkane sulfonates which are characterized by the following structure:

R-O O--N(GHe)nSOsA where A is hydrogen or an alkali metal, i. e., ammonium, sodium, or potassium, n is a small. whole number from one to about five, preferably two or three, R is hydrogen, or an alkyl, aryl, or cycloaliphatic group, such as methyl, and R is an alkyl or alkylene radical, such as myristyl, palmityl, oleyl and stearyl. Sodium palmitic tauride, sodium palmitic methyl tauride, sodium myristic methyl tauride, sodium palmitic-stearic methyl tauride and sodium palmitic methyl amidopropane sulfonate are typical 7 examples thereof.

These compounds are prepared by interacting the corresponding aliphatic acid anhydride or halide with an organic aliphatic aminosulfonic acid, such as taurine, NH CH CH SO H, and the various N-substituted taurines, such as N-methyl taurine, or aminopropane sulfonic acid, NH (CH SO H.

Other water-soluble alkyl aromatic sulfonic acids include those prepared by alkylating benzene or naphthalene with kerosene fraction followed by sulfonation to aliphatic sulfonic acids, esters of sulfuric acid with aliphatic alcohols of ten to eighteen carbon atoms, particularly those derived by the reduction of coconut oil, palm oil and the like long-chain fatty acids, sulfonated castor oil, esters and ethers of isethionic acid, long-chain fatty acid esters and long-chain alkyl ethers of 2,3-dihydroxy propane sulfonic acid and sulfuric acid esters of monoglycerides and glycerol monoethers.

Examples of organic nonionic non-soap detergents include alkyl oxyether and ester and thioether and ester detergents having the following general formula:

where R is a straight or branched chain saturated or unsaturated hydrocarbon group having from eight to eighteen carbon atoms or an aralkyl group having a straight or branched chain saturated or unsaturated hydrocarbon group of from eight to eighteen carbon atoms attached to the aryl nucleus, and attached to A through the aryl nucleus, A is selected from the group consisting of ethereal oxygen and sulfur, carboxylic ester and thiocarboxylic ester groups and x is a number from eight to twenty. R can, for example, be a straight or branched chain octyl, nonyl, decyl, lauryl, myristyl, cetyl or stearyl group, or an alkyl aryl group such as octylbenzene, nonylbenzene, decylbenzene, stearylbenzene, etc.

The sulfated ethoxynated derivatives of the above also are useful anionic detergents:

where M is hydrogen or an alkali metal or organic amine cation and x, A and R are as above.

When R is alkyl it will be evident that the detergent can be regarded as derived from an alcohol, mercaptan, oxy or thio fatty acid of high molecular weight, by condensation with ethylene oxide. Typical of this type of alkyl ether are the condensation products of oleyl or dodecyl alcohol or mercaptan with from eight to seventeen moles of ethylene oxide, such as Emulfor ON, Nonic 218 and Sterox SE and SK. Typical allyl esters are G1226 and Renex (polyoxyethylene ester of tall oil acids), Sterox CD and Neutronyx 330 and 331 (higher fatty acid esters of polyethylene glycol).

When R is aralkyl, the detergent can be derived from an alkyl phenol or thiophenol.

The ethoxynated alkyl phenols and thiophenols have the following general formula:

where R is a straight or branched chain saturated or unsaturated hydrocarbon broup having at least eight carbon atoms up to approximately eighteen carbon atoms, A is oxygen or sulfur and x is a number from eight to twenty. R can, for example, be a straight or branched chain octyl, nonyl, decyl, lauryl, cetyl, myristyl, or stearyl group. Typical are the condensation products of octyl and nonyl phenol and thiophenol with from eight to seventeen moles of ethylene oxide, available commerically under the trade names NIW, Antarox A-400,

Igepal CA and C0, Triton X-100, Neutronyx 600 and Tergitol NFX.

The optional supplemental builders may be alkali metal inorganic salts, typical examples of which include sodium and potassium sulfates, sodium and potassium chlorides, sodium and potassium silicates, and sodium and potassium carbonates.

In addition to or instead of the above-mentioned supplemental inorganic salts, organic materials such as sodium carboxymethylcellulose can be used as builders.

The builder mixture is so chosen among alkaline, neutral, and acidic salts that the composition obtained in an aqueous 014% washing solution has a pH of 7 or above. Preferably, its pH lies within the range from 7 to about 10 since solutions which are more alkaline may be irritating to the skin and tend to weaken some fabrics, particularly woolens. In general, the alkali metal carbonates are preferred agents for bringing the pH of the solution to a high alkaline value within the preferred range.

The heat dried detergent compositions containing a polyphosphate are prepared by conventional methods, as by blending the components thereof in an aqueous solution or slurry and then drying the resulting mixture in a spray or drum dryer at elevated temperatures to any desired moisture content.

The tarnish inhibitor may be added to the polyphosphate composition at any stage of its manufacture, to the finished polyphosphate composition, or to the polyphosphate solution.

It was found that the ferrous salts were ineffective as tarnish inhibitors in liquid polyphosphate detergent compositions.

The compositions of the invention will be further illustrated by the following Examples 144 wherein a typical water-soluble ferrous salt, namely, ferrous ammonium sulfate hexahydrate, was employed. Although these examples for convenience of calculation show the addition stated percentages of ferrous sulfate, it will be understood that an equivalent amount of ferrous ammonium sulfate hexahydrate was actually used. In these examples the following test procedure was employed. A specified amount of the detergent composition was dissolved in somewhat less than one quart of water at a temperature under 170 F., and the ferrous salt then added in the form of an acidified solution containing 0.02 g. of zinc to prevent the oxidation of the ferrous ions. More Water was then added thereto to give a total volume of one quart and the pH adjusted when necessary to 9.5- 9.9. 300 ml. of this solution were placed in a beaker and the solution adjusted within the range from F. to F. A strip of German silver metal, 6" x 1", which had been cleaned with a metal polish and rinsed and dried, was partially immersed in the solution and allowed to remain for one-half hour at 160 F. to 170 F. The metal strip was then removed, rinsed, and dried with a cloth. The strip was visually examined for tarnish and effectiveness of the ferrous salt in inhibiting the formation of tarnish graded as follows:

Grade No.

Degree of Tarnish N o tarnish.

Interface stain only.

Barely noticeable tarnish.

Slight tarnish.

Moderate tarnish.

Considerable (heavy) tarnish,

Severe, as when inhibitor is absent.

Examples l-ll show that the minimum amount of a Water-soluble ferrous salt based on the weight of polyphosphate necessary to inhibit the formation of tarnish upon German silver by an alkali metal polyphosphate will vary depending upon various factors noted above, one of which is the nature of thealkali metal polyphosphate.

Examples 1-11 Percent Ferrous sulfate (polyphosphate basis) 3.3 4.4 5.5 6.7

Polyphosphete Tarnish Grade Tetrasodium pyrophosphate (Examples 1-5) Sodium hexametaphosphate (Examples 6-8) Hexasodium tetrapolyphosphate (Examples 9-11) 6 6 0 A water-soluble ferrous salt is efiective as a tarnish inhibitor in polyphosphate compositions which contain an organic nonsoap detergent as shown by Examples 12-15. It will be noted from a comparison with Example 2 that the organic nonsoap detergent serves to enhance the tarnish inhibiting properties of the water-soluble ferrous salt.

Examples 12-15 0.9 g. of sodium dodecylbenzenesulfonate and 2.25 g. of pentasodium tripolyphosphate were dissolved in distilled water, and 6.7% of ferrous sulfate based on the weight of the polyphosphate added thereto, and the solution diluted to a volume of one quart. This solution tarnished German silver only to grade 3, while an identical solution without the presence of the ferrous sulfate tarnished German silver to grade 6. Tetrasodium pyrophosphate was substituted for the same amount of the pentasodium tripolyphosphate in the above composition using 3.3% of ferrous sulfate based on the weight of polyphosphate. A strip of German silver metal placed in the solution of the composition containing ferrous sulfate was tarnished only to grade 1, whereas a strip of German silver metal placed in a solution of the composition without the presence of the ferrous sulfate tarnished to grade 6. It wil be noted that an identical solution except for the presence of sodium dodecylbenzenesulfonate tarnished to grade (Example 2).

Water-soluble ferrous salts display an enhanced antitarnishing activity against certain alkali metal polyphosphates in the presence of an alkali metal silicate as shown below in Examples 16-17.

Examples 16-17 2.25 g. of tetrasodium pyrophosphate and 0.5 g. of sodium silicate solids were dissolved in distilled water, and 2.2% of ferrous sulfate based on the weight of the polyphosphate added thereto, and the solution diluted to a volume of one quart. This solution tarnished German silver only to grade 3, while an identical solution without the presence of ferrous sulfate tarnished German silver to grade 6. A comparison of these examples also with Example 2 will show the enhanced anti-tarnishing activity of water-soluble ferrous salt against an alkali metal polyphosphate when an alkali metal silicate is present in the composition.

The addition of a water-soluble ferrous salt to a polyphosphate composition containing an organic nonsoap detergent, which may be either anionic, nonionic or cationic, as well as supplemental builders, inhibits the formation of tarnish by such detergent compositions. This is clearly illustrated by the examples set forth below wherein the following two compositions, or specified modifications thereof, were employed.

Composi- Composition X tion Y Sodium Dodeeylbenzenesulfonate 18. 0 l8. 0 Tetrasodium Pyrophosphate 45.0 Pentasodium Tripolyphosphate 45. 0 Sodium Carbonate 3.0 3.0 Sodium Silicate 6.0 6. 0 Sodium Carboxymethyloellulose. 0. 5 0. 5 Water 7.0 7. 0 Sodium Sulfate and Misc. Inert. Mater1als. 20. 5 20. 5

In compositions X and Y the amounts of the various components are expressed in percent by weight.

Examples 18-26 To 5 g. each of compositions X and Y there was added ferrous sulfate in the proportions shown below and the test procedure carried out with the following results:

Percent Ferrous Sulfate (poly- Examples 18-26 show that the minimum amount of a water-soluble ferrous salt necessary to inhibit the formation of tarnish by polyphosphate compositions containing an organic anionic nonsoap detergent and supplemental builders will vary depending upon the nature of the alkali metal polyphosphate present in the composition and also show that an organic nonsoap detergent and an alkali metal silicate enhance the tarnish inhibition action of a water-soluble ferrous salt.

A ferrous salt is effective as a tarnish inhibitor in polyphosphate compositions containing an organic nonsoap detergent as well as supplemental builders when the alkali metal polyphosphate is other than tetrasodium pyrophosphate or pentasodinm tripolyphosphate, for example, sodium hexametaphosphate and hexasodium tetrapolyphosphate. This is clearly illustrated by Examples 27-30 set forth below.

Examples 27-30 Sodium hexametaphosphate and hexasodium tetrapolyphosphate were separately substituted for the same amount of tetrasodium pyrophosphate in composition X and the two compositions tested in accordance with the test procedure. 5 g. of each of these compositions in a quart of water tarnished German silver to a grading of 6, i. e., severe tarnish. When 6.7% of ferrous sulfate, based on the weight of polyphosphate, was added to each of these compositions, the tarnish grading of both compositions upon German silver was reduced to grade 1 indicating interface stain only.

A water-soluble ferrous salt is also effective as a tarnish inhibitor in polyphosphate compositions containing other organic anionic nonsoap detergents as well as supplemental builders as shown by Examples 31-34.

Examples 31-34 The organic anionic nonsoap detergents, the sodium salt of N-palmitoyl-N-methyl taurine and sodium-3-dodecyloxy 2 hydroxypropanesulfonate, were substituted separately for the same amount of sodium dodecylbenzenesulfonate in composition X. When 5 g. of each of these compositions was tested in accordance with the test procedure, both compositions tarnished German silver to grade 6, indicating severe tarnish. The tarnish was reduced to grade 2 in both instances when 2.2% of ferrous sulfate based on the weight of polyphosphate was included in each of the two compositions. i

A ferrous salt is also effective as a tarnish inhibitor in polyphosphate compositions containing either an organic cationic nonsoap detergent or an organic nonionic nonsoap detergent as well as supplemental builders, as illustrated in Examples 35-38.

Examples 35-38 prepared by condensing ethylene oxide with a hydrophobic base formed by the condensation of propylene oxide with propylene glycol where b is an integer selected from the group consisting of 26 to 30 and a-l-c is an integer such that the molecule contains from 40% to 50% of ethylene oxide, was substituted for the sodium dodecylbenzenesulfonate in composition X. g. of each of these compositions when dissolved in one quart of water and tested in accordance with a test procedure tarnished German silver to grade 6. When 2.2% ferrous sulfate based on the weight of polyphosphate was added to each of these compositions, they both then had a tarnish grading of 2, indicating barely noticeable tarnish.

As noted above the water-soluble ferrous salts are effective as tarnish inhibitors in polyphosphate compositions containing an organic nonsoap detergent as well as supplemental builders wherein the alkali metal polyphosphate may vary within the range of about 5% to about 50%. Data showing the effect of the reduction in the amount of the alkali metal polyphosphate present in the detergent composition is set forth below in Examples 39-40.

Examples 39-40 Composition X was modified by employing 5% of tetrasodium pyrophosphate therein with the remainder of the composition being the same with the exception that the amount of sodium sulfate was increased to offset the corresponding decrease in the tetrasodium pyrophosphate content. 5 g. of the modified composition dissolved in a quart of distilled water having a temperature of 160 F 170 F. had a tarnish grading upon German silver of grade 4. When 2.2% of ferrous sulfate based on the weight of tetrasodium pyrophosphate was added to the composition and 5 g. thereof dissolved in a quart of water, the composition had a tarnish grading of 2 upon German silver metal, indicating considerable improvement.

The amount of the organic nonsoap detergent present in the polyphosphate composition may be varied within the range from about 5% to about 40% as noted above and as further illustrated by Examples 4l;42.

Examples 41-42 5% of sodium dodecylbenzenesulfonate was employed in composition X with the amount of sodium sulfate being increased to offset the decrease in the sodium dodecylbenzenesulfonate content of the composition. 5 g. of this modified composition dissolved in a quart of distilled water had a tarnish grading of 6 upon German silver metal, whereas 5 g. of the composition which also contained 2.2% of ferrous sulfate based on the weight of the polyphosphate had a reduced tarnish grading of 2.

Examples 43-44 illustrate the fact that the ferrous salts are effective as tarnish inhibitors in polyphosphate compositions when the polyphosphate compositions are used in hard water. It will be noted that in all of the previous examples the water was soft water, i. e., distilled water.

Examples 43-44 5 g. of composition X dissolved in a quart of water having a hardness of p. p. m. tarnished German silver to grade 6, whereas 5 g. of composition X containing 2.2% of ferrous sulfate based on the weight of polyphosphate dissolved in a quart of water having a hardness of 180 p. p. m. tarnished German silver only to grade 2. When ferrous sulfate was employed as a tarnish inhibitor rather than ferrous ammonium sulfate comparable results were obtained as shown by Examples 45-49 below.

Examples 45-49 To 5 g. each of composition X there was added ferrous sulfate in the proportions shown below and the test procedure carried out with the following results:

Percent Ferrous Sulfate (polyphosphate basis) Tarnish Grading 6 Obviously many modifications and variations may be made in the invention herein set forth Without departing from the spirit and scope thereof, and only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A heat dried detergent composition consisting essentially of a water-soluble alkali metal polyphosphate selected from the group consisting of tetrasodium and tetrapotassium pyrophosphates, sodium and potassium hexametaphosphates, and hexasodium and hexapotassium tetrapolyphosphates which in aqueous solution tarnishes German silver; and a water-soluble ferrous salt in an amount to lessen the tarnishing action of the polyphosphate.

2. A heat dried detergent composition consisting essentially of an alkali metal pyrophosphate which in aqueous solution tarnishes German silver and at least about 4% by weight of a water-soluble ferrous salt based on the weight of the pyrophosphate.

3. A heat dried detergent composition consisting essentially of an alkali metal hexametaphosphate which in aqueous solution tarnishes German silver at least about 7% by weight of a water-soluble ferrous salt based on the weight of the hexametaphosphate.

4. A heat dried detergent composition consisting essentially of an alkali metal tetrapolyphosphate which in aqueous solution tarnishes German silver and at least about 7% of a water-soluble ferrous salt based on the weight of the tetrapolyphosphate.

5. A heat dried detergent composition as set forth in claim 1 wherein the water-soluble ferrous sale is ferrous ammonium sulfate.

6. A heat dried detergent composition consisting essen tially of from about 5% to about 50% of an alkali metal polyphosphate which in aqueous solution tarnishes German silver, from about 5% to about 40% of an organic nonsoap detergent, and a water-soluble ferrous salt in an amount to lessen the tarnishing action of the polyphosphate.

7. A heat dried detergent composition as set forth in claim 6 wherein the water-soluble ferrous salt is ferrous ammonium sulfate.

8. A heat dried detergent composition as set forth in claim 6 wherein the water-soluble ferrous salt is ferrous sulfate.

9. A heat dried detergent composition consisting essentially of from about 5% to about 50% of an alkali metal tripolyphosphate which in aqueous solution tarnishes German silver, from about 5% to about 40% of an organic nonsoap detergent, and a water-soluble ferrous salt in an amount of at least about 4% based on the weight of the tripolyphosphate and suflicient to inhibit such tarnishing.

10. A heat dried detergent composition consisting essentially of from about 5% to about 50% of an alkali metal pyrophosphate which in aqueous solution tarnishes German silver, from about 5% to about 40% of an organic nonsoap dfi firgellt, and a water-soluble ferrous salt in an amount of at least about 1.7% based on the weight of the pyrophosphate and sufficient to inhibit such tarnishing.

11. A heat dried detergent composition consisting essentially of from about 5% to about 50% of an alkali metal hexametaphosphate which in aqueous solution tarnishes German silver, from about 5% to about 40% of an organic nonsoap detergent, and a water-soluble ferrous salt in an amout of at least about 1.7% based on the weight of the hexametaphosphate and sufiicient to inhibit such tarnishing.

12. A heat dried detergent composition consisting essentially of from about 5% to about 50% of an alkali metal 10 tetrapolyphosphate which in aqueous solution tarnishes German silver, from about 5 to about 40% of an organic nonsoap detergent, and a water-soluble ferrous salt in an amount of at least about 1.7% based on the weight of the tetrapolyphosphate and sufiicient to inhibit such tarnishing.

References Cited in the file of this patent UNITED STATES PATENTS 2,618,603 Schaeffer Nov. 18, 1952 2,618,604 Schaefter Nov. 18, 1952 2,764,242 Rohrback Sept. 25, 1956

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2618603 *Feb 4, 1949Nov 18, 1952Procter & GambleDetergent compositions containing metal discoloration inhibitors
US2618604 *Nov 25, 1949Nov 18, 1952Procter & GamblePolyphosphate-containing detergent compositions having decreased corrosivity toward aluminum
US2764242 *Apr 29, 1953Sep 25, 1956Gilson H RohrbackPrevention of casing corrosion
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5512201 *Feb 13, 1995Apr 30, 1996Applied Chemical Technologies, Inc.Solder and tin stripper composition
Classifications
U.S. Classification510/401, 510/477, 510/233, 510/228, 510/488, 252/387, 510/457, 510/235, 510/335, 510/255, 510/534, 510/508
International ClassificationC11D3/06, C23G1/20, C11D3/02
Cooperative ClassificationC11D3/06, C11D3/046, C11D3/0073, C23G1/20
European ClassificationC11D3/04S, C11D3/00B15, C11D3/06, C23G1/20