FOOD PRESERVATIVES. 107 



(d) POTASH AM) SODA. a 



Evaporate an aliquot portion of the solution, prepared as described, nearly to dry- 

 ness to remove the excess of hydrochloric acid, dilute, and heat to boiling. While 

 still boiling, add barium chloride solution as long as a precipitate forms and enough 

 barium hydrate to make the liquid strongly alkaline. As soon as the precipitate has 

 settled, filter and wash with hot water, heat the filtrate to boiling, add sufficient 

 ammonium carbonate solution (1 part of ammonium carbonate in 5 parts of 2 per 

 cent ammonia water) to precipitate all the barium, filter, and wash with hot water. 

 Evaporate the filtrate to dryness, ignite below redness to remove ammonia salts. 

 Add to the residue a little water and a few drops of ammonium carbonate solution. 

 Filter into a tared platinum dish, evaporate, ignite below redness, and weigh the 

 mixed potassium and sodium chlorids. 



Determine the potash as potassium platinichlorid, using the factors 0.1939 for K 2 O 

 and 0.3069 for KC1. 



13. DKTKKM I NATION ol 1'lIoSPHORIC AdD. 



Mix 5 grams of the material with a little magnesium-nitrate solution, dry, ignite, 

 and dissolve in hydrochloric acid. In an aliquot of the solution determine phos- 

 phoric acid as magnesium pyrophoephate by the molybdic method. 1 ' 



14. DETERMINATION 01- si I.IMII UK AC-ID. 



Boil 5 grams of the powder gently for one and one-half 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 100 cc, dilute considerably, precipitate with barium chlorio!, 

 filter through a Gooch crucible, ignite, and weigh. Direct solution of the material 

 without burning of the organic matter was proposed by Crampton. c The dextrose, 

 formed by the action of the acid on the starch of baking powders, does not interfere 

 with the accuracy of the process.' 1 



15. DETERMINATION OF AMMONIA. 



Ammonia alum is often an ingredient of cream-of-tartar substitutes and baking 

 powders, and ammonium carbonate is occasionally present in baking powders. Deter- 

 mine ammonia by distillation with caustic soda into standard acid and tit-ration. 



XVI. FOOD PRESERVATIVES. 



By W. M. ALLKN, 

 Stotfe Department of Agriculture, I!<t/,lflh, N. C. 



1. DETECTION OF FORMALDEHYDE, 

 (a) PREPARATION OF SAMPLE. 



If the material be solid or semisolid, macerate from 200 to 300 grams in a mortar 

 with about loo cc of water until a sufficient degree of fluidity is obtained. Take the 

 sample so prepared and make distinctly acid with phosphoric acid. Transfer to a 

 short-necked distilling flask of copper or glass of from 500 to 800-cc capacity. If a 

 copper flask is used, the heat can be applied directly; if the flask be glass, it is best 

 to heat in a linseed-oil bath. Connect flask with glass condenser and distill off from 

 40 to 50 cc. In the case of liquids, acidify from 200 to 300 cc with a strong excess of 

 phosphoric acid, and distill as directed under 3. 



Src Appendix, p. 160. 



' I". S. Drpt. of Atfr.. Div. of ('hem., Kill. 1C, revised, p. 12. 

 -I'. S. Dcpt. of ART-.. Div. of Clu-in.. Bui. 1:>, purl :>. p. 596. 

 'Conn. Atfr. Kxpl. Sin., Urp. 1 ( .M)<, p. 111). 



