Molybdate solution: 44 grams ammonium heptamolybdate in 250 cc. Citric acid solution: 50 grams citric acid in 500 cc. Magnesium sulphate solution: 60 grams MgSO4. 7H2O in 500 cc. Ammonia solution: 80 cc. concentrated ammonia (sp. gr. o.880) in 500 cc. Hydrochloric acid: 60 cc. concentrated hydrochloric acid in 500 cc. Methyl orange solution: (b) Process.-An amount of material containing not more than 0.2 gram tatraric acid, not more than 0.3 gram alum, and not more than 0.3 gram calcium superphosphate, is accurately weighed, and placed in a dry flask. To this, 5 cc. of citric acid and 10 cc. of molybdate solution are added, and allowed to react with the substance for 10 or 15 minutes (with an occasional shake). Next, 5 cc. of magnesium sulphate solution are added, and 15 cc. of ammonia solution stirred in. After a few minutes (not more than one hour), the solution is filtered through a dry filter, a slight turbidity of the filtrate being disregarded. To 20 cc. of the filtrate are then added a few drops of methyl orange and hydrochloric acid, from a burette, till the pink color appears (2 or 3 drops too much or too little are of no consequence). Finally, 10 cc. more of the molybdate solution are added to the pink solution, which now becomes colorless or pale yellow, and water is added to make up the volume to 50 cc. This solution, after filtering if necessary, is polarized in a 20-cm. tube. The amount of tartaric acid in grams (y) in the weight of substance originally taken is given by the following formula, in which x is the rotation in minutes: y=0.001086x+0.001601√x. But if the rotation is not less than 40', the simpler formula, may be employed. y=0.0075 +0.001168x, The following table gives the tartaric acid in grams for every 10 minutes Determination of Starch.-McGill's Method (Modified).-Digest I gram of the sample with 150 cc. of a cold 3% solution of hydrochloric acid during twenty-four hours, with occasional shaking. Filter through a tared Gooch crucible, wash first with water until neutral, then once with alcohol, and finally with ether. Dry at 110° C. for four hours, cool, and weigh. Burn off the starch, and again weigh. The difference in the two weights indicates the weight of the starch. The purity of the starch is insured by examination with the microscope. Acid Conversion Method.†-If the sample contains lime, mix 5 grams in a 500-cc. flask with 200 cc. of 3% hydrochloric acid, and let the mixture stand an hour with frequent shaking. Filter through a wetted 11-cm. filter, wash with water, and transfer the starch by a wash-bottle from the filter-paper back into the original flask, using 200 cc. of water. If the sample be free from lime, weigh 5 grams directly into the 500-cc. flask with 200 cc. of water. In either case add 20 cc. of hydrochloric acid (specific gravity 1.125) and heat the flask in boiling water for 21 hours, the flask being provided with a reflux condenser. Determine the dextrose, and from this the starch in the regular manner. Detection of Aluminum Salts.‡-(a) In Baking Powder.-Appli cable in presence of phosphates. Burn to an ash about 2 grams of the sample in a platinum dish. Extract with boiling water and filter. Add to the filtrate sufficient ammonium chloride solution to produce a distinct odor of ammonia. A flocculent precipitate indicates aluminum. In igniting, as above directed, sodium aluminate results from the more or less complete fusion. The reaction which occurs may be represented as follows: Na,Al2O1+2NH ̧Cl+4H2O=Al2(OH),+2NH ̧OH+2NaCl. If any phosphate of lime be present, it will be insoluble in the solution of the ash. If phosphate of sodium or potassium be present, it will go into solution, but will only precipitate out when an aluminum salt is also present on the addition of the ammonium chloride reagent. (b) In Cream of Tartar.-Mix about 1 gram of the sample with an equal quantity of sodium carbonate, burn to an ash, and proceed as in the case of baking powder (a). * Canada Inland Rev. Bul. 68, p. 33. † U. S. Dept. of Agric., Bur. of Chem., Bul. 65, p. 105; Bul. 107 rev., p. 176. Determination of Alumina.-The above qualitative method with ammonium chloride may be made quantitative in presence of phosphates as follows: After carrying out the qualitative method as above directed, filter off the final precipitate, dissolve it in nitric acid, and test it for phosphate with ammonium molybdate. If phosphates are found absent, proceed as before with a weighed amount of the sample and wash, ignite, and weigh the residue as Al2O3. If phosphate is found present in the ammonium chloride precipitate, proceed as before, igniting and weighing the total residue. Then determine the P2O, in the latter and subtract from the total. The difference will be the Al2O3. Determination of Lime.-5 grams of the sample are treated in a 500 cc. graduated flask with 50 cc. of water and 25 cc. of concentrated hydrochloric acid. Add water to the mark, shake, and allow the starch to settle. Decant through a dry filter, and to 50 cc. of the filtrate add ammonia nearly to neutralization, an excess of ammonium acetate solution, and 4 cc. of 80% acetic acid, and heat at 50° C. Filter if necessary, and precipitate the lime with an excess of ammonium oxalate. Filter, wash, and ignite over a blast-lamp. Weigh as CaO. Determination of Potash and Soda.*-Weigh out 5 grams into a platinum dish, and incinerate in a muffle at a low heat. The charred mass is well rubbed up in a mortar, then boiled fifteen minutes with about 200 cc. of water, to which has been added a little hydrochloric acid. The whole is transferred to a 500-cc. flask, and, after cooling, made up to the mark and filtered. Of the filtered liquid 100 cc., representing 1 gram of the sample, are measured out, heated to boiling, and a slight excess of barium chloride solution added; then without filtering barium hydroxide is added in slight excess, the precipitate filtered off, and washed. To the filtrate is added a little ammonium hydroxide, and ammonium carbonate solution until the barium is precipitated. This precipitate is filtered and washed, the filtrate evaporated to dryness, and carefully ignited below redness until all volatile matter is driven off. The residue is dissolved in a few cc. of water, and a few drops of ammonium carbonate solution added. The precipitate, if any, is removed by filtering and washing, and the filtrate evaporated in a small tared platinum dish, ignited below redness, and weighed. * Conn. Agric. Exp. Sta. Rep., 1900, p. 178. This gives the weight of the mixed chlorides. The residue is taken up with hot water, from 5 to 10 cc. of a 10% solution of platinic chloride added, and the whole evaporated to a sirupy consistency on the waterbath; it is then treated with 80% alcohol, the precipitate washed with 80% alcohol by decantation, transferred to a Gooch crucible, dried at 100° C., and weighed. The weight of the precipitate, multiplied by 0.19308, gives the weight of K2O, and by 0.3056 the equivalent amount of KCl. The weight of KCl found is subtracted from the weight of the mixed chloride, the remainder being NaCl, which, multiplied by 0.5300, gives the weight of Na2O in the sample. Determination of Phosphoric Acid.-Mix 5 grams of the material with 10 cc. of magnesium nitrate solution, prepared by dissolving calcined magnesia in nitric acid, adding magnesia in excess, and filtering, dry, ignite, and dissolve in hydrochloric acid. Remove an aliquot part of the solution, corresponding to 0.25 gram, 0.50 gram, or I gram, neutralize with ammonia, clear with a few drops of nitric acid, and proceed according to the usual method, precipitating successively with molybdic solution and magnesia mixture. Determination of Sulphuric Acid.-Boil 5 grams of the powder gently for 1 hours with a mixture of 300 cc. of water and 15 cc. of concentrated hydrochloric acid. Dilute to 500 cc., draw off an aliquot portion of ICO cc., dilute considerably, precipitate with barium chloride, filter through a Gooch crucible, ignite, and weigh. Direct solution of the material without burning the organic matter was proposed by Crampton.* Determination of Ammonia (present in the form of ammonia alum or ammonium carbonate). Mix 5 grams of the sample with 200 cc. of water, and add an excess of sodium hydroxide. Distil into standard acid, and determine the ammonia by titration. Detection and Determination of Arsenic.-Proceed according to the Marsh or Sanger-Black-Gutzeit method without preliminary treatment (page 64). Determination of Lead.-Method of the Victor Chemical Works.-In the case of phosphate and alum phosphate powders and of acid phosphate weigh 1 to 2 grams of the material into a small beaker, add 10 to 15 cc. of water and 2 to 3 cc. of concentrated sulphuric acid. Bring to a boil and if starch is present continue the heating on a water bath until the starch is hydrolized, replacing the water lost by evaporation. Cool, * U. S. Dept. of Agric., Div. of Chem., Bul. 13, part 5, p. 596. add 30 to 40 cc. of 95% alcohol, stir and allow to stand over night. If a precipitate of sodium aluminum sulphate appears, due to an excess of alcohol, add water in small amounts until dissolved. Filter and wash with 75 to 80 cc. of alcohol until free from acid. Dry, transfer the bulk of the precipitate to a crucible, digest with hot alkaline ammonium acetate solution (390 grams of ammonium acetate in 1800 cc. of water and 150 cc. of concentrated ammonium hydroxide), filter through the paper previously used, and wash with small portions of the hot solution. After cooling, make up to 50 cc., add 1 cc. each of 10% potassium, cyanide solution, 1% gelatine solution, and colorless ammonium sulphide solution. Compare with standard lead solution prepared from a stock solution of 0.160 gram of lead nitrate (dried over sulphuric acid) in 1000 cc. of water (1 cc.=0.0001 gram Pb) and the quantities of alkaline acetate, cyanide, gelatine and sulphide already given. In the case of tartrate powders and cream of tartar shake 10 grams of the material with 50 cc. of water and 40 cc. of 2N ammonia water. Make up to 100 cc., mix and filter through a dry filter. Determine lead colorimetrically in 50 cc. of the filtrate as above, omitting the preliminary precipitation as sulphate. The standard lead solution should be made up using about the same amount of lead-free cream of tartar as in the solution of the material. SEMOLINA AND EDIBLE PASTES. Semolina is the coarse meal ground from certain varieties of hard or "durum" wheats, grown originally in Italy, Sicily, and Russia, but at present in France and certain parts of the United States and Canada. This hard wheat is high in gluten, and especially adapted for the preparation of macaroni and the various pastes. A peculiar process is employed in preparing the wheat, whereby the husk is removed by wetting, heating, grinding, and sifting, the resulting meal or semolina, being in the form of small, round, glazed granules. Italian Pastes.-Semolina furnishes the basis of the Italian edible pastes, being mixed with warm water, kneaded, and molded into various forms, either by pressure through holes in an iron plate, or otherwise, and finally dried. In parts of Italy juices of carrots, onions, and other vegetables are said to be mingled with the paste, but for local consumption |