Determination of Potash in Fertilizers or Base Goods In the Absence of Ammonium Salts and Organic Matter PHILIP McG. SHUEY, Shuey & Company, Savannah, Ga.
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HE proposed method for determining potash in fertilizers and base goods removes the calcium, iron, and aluminum as phosphates. after boiling in water, instead of removing the calcium as oxalatc. Only one subsequent evaporation and no ignition are necessary; therefore there is no possible loss of K*O by derrepitation or volatilization and the time and attention required in these operations are saved. In short, the determination is the same as in the case of potash salts, except that a little mono-, di-, or trisodium phosphate or phosphoric acid is added, followed by the addition of dilute sodium hydroxide until the solution is permanently alkaline to litmus. A small amount of additional phosphate or phosphoric acid is needed to effect complete precipitation of the calcium, because calcium occurs in phosphate rock and superphosphate in excesa of the PZO, required to combine with it. The method has been found repeatedly to yield very accurate and concordant results in the absence of ammonium salts and organic m a t t e r - e . g., in mixtures of superphosphate and potash ealts. The test for the presence of ammonia may be made in an instant by simply adding sodium hydroxide to a hot aqueous solution of a portion of the sample and noting the odor. The appearance and odor of the sample itself will at once reveal the presence or absence of organic matter such as tankage, vegetable meal, etc. The method is particularly useful because it is necessary for a manufacturer first to make a base when using considerable quantities of potassium sulfate, owing to the setting properties of the sulfate. Five grams of the prepared sample are transferred to a 500-ml. flask, or 2.5 grams to a 250-ml. flask, and boiled for half an hour with approximately 350 or 200 ml., respectively, of distilled water; 30 ml. of a 2 per cent solution, or 6 ml. of a 10 per cent solution, of sodium p h i ~ p h a t eare added, followed by dilute sodium hydroxide while the flask is whirled until the solution is permanently alkaline to litmus. If the solution again becomes acid on standing, more sodium hydroxide should be added, avoiding a large excess. The fladk is then allowed to cool, the solution is made up t o the mark, mixed, and filtered, and an aliquot of 25 ml., equivalent to 0.25 gritm, is pipetted into a casserole or dish other than platinum; the platinic chloride and a few dro s of hydrochloric acid are added, and the determination is compreted according to the official method for KzOin potash salts (5’). dust before filterin , it is advisable to grind the precipitate lightly a i t h a small pestfe in order to remove excess platinum chloride and facilitate subsequent purification with ammonium chloride solution.
The strength of the alcohol used in all cases was 95 per cent. According to Scott (2)“too large a volume of alcohol should be avoided, as KrPtCb is slightly soluble in alcohol, especially that of 80 per cent. For this reason 95 per cent alcohol is preferable for the washing.” Fresenius states that “potassium platinic chloride is not absolutely insoluble even in strong alcohol.” Since the Lindo-Cladding method of purifying the precipitate is effective, the presence of a small amount of lime does not interfere. For instanre, 20.23per cent KIO was found in the sample of potassium sulfate base when all the calcium had not been procipitated, compared with 20.20 per cent when precipitation waa complete. When a large excess of platinum chloride is not added, some of the sodium will form sodium platinic chloride (NarPtCL) and some may remain as sodium chloride. In either case, the sodium is freed from the precipitate when the official method is followed. Equal weights of pure sodium chloride and pure potassium chloride were boiled in a flssk with water, and slightly more platinum chloride was added to the aliquot than that required to combine with the potash; the result was 63.18 per cent KIO as against 63.17 per cent theory. A large excess of platiQic chloride is unnecessary. It is only necessary to have such exresa as is readily shown by the color after evaporation, especially after the acidified alcohol has been added. The dish or casserole should be removed from the steam bath soon after evaporation, in order to prevent the formation of insoluble compounds. The addition of a small amount of glycerol has been recommended, but the author has not investigated this point. While the weighed portions of the samples were being boiled with water, they had a tendency to ball or lump, retarding or preventing complete extraction of the potash. In the case of the triple superphosphate base sample, lumping persisted throughout the entire half-hour boiling period. When the solution was made by adding altcrnately small portions of the weighed charge of the sample and water, and quickly giving the flask a whirl immediately after each addition of water, there was no caking during boiling. It appears that lumps of calcium sulfate, which is not
TABLEI. DETERMINATION OF POTASH
Table I reports determinations made to show the accuracy of the method. Contamination amounting to 0.15 per cent due to dissolved silicates was found in the caustic soda in the case of base goods containing superphosphate made from Florida rock; therefore this amouiit was deducted. It is advisable to know the amount of dissolved glass in the sodium hydroxide used when not freshly made up and to make the necessary correction when the precipit a t e is not dissolved with hot water. I n analyzing the samples of base goods containing superphosphate made from Tennessee brown rock and triple superphosphate made from Idaho rock, fresh sodium hydroxide solution was made up from pure sticks; no silica whatever was found in the precipitates. All precipitates from these determinations were dissolved in hot water, and after drying, the Gooch crucibla were found to weigh the same as they did originally.
Kz0 O5cial
KzO Modified
%
%
Base goods made in proportion of 1255 pounds of su er 2 0 . 0 2 phosphate and 745 pounds of c. P. KzSO4, having tfeo: 20.05 retical analysis of 20.13%. Superphosphate from Florida land pebble rock AV.
Base goods made in proportion of 1255 ounds of superphosphate and 745 pounds of c. P. K,gOd having theoretical analysis of 20.13%. Superphdsphate from Tennessee brown rock Av. Base goods made in proportion of 1255 pounds of triple superphos hate and 745 pounds of c. P. K B O r having theoretics? analysis of 20.13%. Triple suierphosphate from Idaho rock Av. Potassium sulfate-magnesia base. Superphosphate from Florida land pebble rock Av.
633
20.20 20.21
20.035 20.24 20.24
20,205 20.20 20.15
20.24 20.31 20.32
20.175 20.32 20.37
20.315 11.05 10.93 10.99
20.345 10.97 10.95 10.96
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634
very soluble in either hot or cold water, are formed by the reaction between monocalcium phosphate and potassium sulfate. The fact that triple superphosphate is very high in monocalcium phosphate supports this view. The reaction may be expressed as follows: Ca(H2POI)z
+ KnSO,
=
Cas04
+ 2IiH1PO4
A weighed portion is boiled with ammonium oxalate according to the official method to prevent loss by the action of the colloids, but in the case of high-analysis base goods, the potassium sulfate has the same effect, and complete recovery of the potash is obtained. In making up the 20 per cent base mixtures, the same kiod and amount of potassium sulfate were used in all cases. The slightly
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different results may largely be ascribed to differences in composition of the phosphate rock deposits. According to Jacob et al. (I), Florida land pebble phosphate contains 0.19 per cent Kz0 (average of 11 analyses), Tennessee brown rock phosphate 0.435 per cent (average of 6 analyses), and Idaho phosphate 0.44 per cent (average of 3 analyses). While the potash is originally present mainly as silicates, a small amount is probably decomposed by the action of fluorine in the mixing pan and during subsequent curing.
Literature Cited (1) Jacob, K.D., Hill, W. L., Marshall, H. L., and Reynolds, D. S., U. S. Dept. Agr., Tech. Bull. 364 (1933). (2) Scott, W. W., “Standard Methods of Chemical Analysis”, 4th~ ed., p. 410, New York, D. Van Nostrand Co., 1925.
Fluorometric Determination of Riboflavin in Pork Products WALTER J. PETERSON, D. E. BRADY, AND A. 0. SHAW Department of Animal Industry, North Carolina Agricultural Experiment Station, Raleigh, N. C.
A method developed for the fluorometric determination of riboflavin in pork and pork products has been applied successfully to ham, pork muscles, fat, liver, heart, lung, and spleen. It is in close agreement with other fluorometricprocedures and the results do not differ greatly from values reported for the same tissues when analyzed by bioassay or microbiological procedures. The adsorption procedure of Conner and Straub and the permanganate oxidation step have been eliminated, thus shortening the time required for analysis. Large differences were found in the riboflavin content of different muscles of the same pig. Appreciable amounts of riboflavin were found in various pork fats from which all lean had been removed.
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HE most widely used procedures for the determination of
riboflavin in meats and meat products have been the biological rat growth assay (3, 7 , 8, 10) and the microbiological procedure of Snell and Strong ‘16). The latter method measures the influence of riboflavin on both the cell growth and the acid production of Lactobacillus casei e grown on a synthetic medium free of riboflavin. The fluorometric method, which measures the degree of fluorescence given by riboflavin in violet light, is being used with success in the analysis of many foods (6,9,18,16), but its application to animal tissue has been only partially successful (Z4,18).For many reasons, the application of fluorometric methods to all types of foods and biological materials seems desirable. All the proposed methods have certain limitations: The biological procedure is expensive m d time-consuming and in some food materials there is the question of the availability of riboflavin (11 ) . In the fluorometric method, excessive turbidity and the presence of extraneous fluorescent materials in solution are troublesome features. Extracts of certain biological material may exert either inhibitory or stimulating effects (17) in the microbiological procedure. Both the fluorometric and microbiological methods have in common the problem of bringing the vitamin into solution. As
existing methods become refined, these and other difficulties will be overcome. Mickelsen, Waisman, and Elvehjem (IS), using the microbiological method, have made extensive investigations of the riboflavin content of meat and meat products. These workers point out that the values in the literature previous to 1934 on the distribution of riboflavin are not of a quantitative nature. Williams and the University of Texas group (17), using the same method, have made important contributions in studies of the vitamin content of tissues and foods. Of particular value to workers in this field is their demonstration of the variability in efficacy of extraction of the different vitamins depending on the nature of the food, the enzyme used, and the heat treatment involved. Of the fluorometric procedures reported, that of Conner and Straub (4) appears to give reliable results with many plant products. This procedure was, therefore, taken aa a starting point in the present studies, and the optimal conditions were determined for its application to pork products. The method which was finally devised differs from the Conner and Straub method in the following points: The adsorption procedure and permanganate oxidation steps have been omitted; the incubation period with clarase has been increased from two hours to 24 hours; and “blank” values are obtained by reduction of the riboflavin of the extracts with sodium hydrosulfite.
Description of Method Because of the sensitivity of riboflavin to light, all manipulations are conducted in a semidarkened laboratory; and amber glassware is used throughout. A 10- to 20-gram sample is dropped into 100 cc. of 0.04 N sulfuric acid in a Waring Blendor and macerated for 2 minutes a t high speed. The creamy mixture is then transferred quantitatively to a 250- or 300-cc. Erlenmeyer flask, using a minimum amount of watcr from a wash bottle to effect the transfer. The flask is plugged with cotton and autoclaved 15 minutes a t 6.8 kg. (15 pounds) pressure. As soon as the flask has cooled, 20 cc. of a 2.5 per cent solution of clarase (4) freshly prepared in a sodium acetateacetic acid buffer are added. [The buffer solution (pH 4.5) is prepared by adding 54.4 cc. of glacial acetic acid to 66.9380 grams of anhydrous sodium acetate together with sufficient distilled water to obtain a solution of the reagents, and then transferred to a I-liter volumetric flask and made up to volume with distilled water.] The contents of the flask are mixed thoroughly
