596 FOODS AND FOOD ADULTERANTS. 



aliquot parts of the filtrate for precipitation ; iti phosphate powders not 

 more than 50 cubic centimeters should be used. Nearly neutralize with 

 ammonia, acidify slightly with acetic acid, add ammonia acetate, and 

 boil. Filter from the precipitate, if there be any, add ammonium ox- 

 alate, and allow to stand several hours. Filter into a Gooch crucible, 

 and dry at 100. Weigh as oxalate. 



ESTIMATION OF SULPHURIC ACID. 



The sulphuric acid was estimated without previous ignition of the 

 powder, as follows : 



Weigh out .5 to 1 gram of the powder, according to its character, the 

 former quantity being more convenient for alum powders, and transfer 

 to a beaker. Digest with strong hydrochloric acid until all of the pow- 

 der, including the starch, goes into solution ; add barium chloride to 

 slight excess while still hot, and allow it to stand for twelve hours, or 

 over night. Filter through a Gooch crucible, ignite, and weigh. 



ESTIMATION OF AMMONIA. 



Ammonia is present either as bicarbonate, or as ammonium sulphate 

 in the alum powders. The estimation was made by the Kjeldahl 

 method, as used by the Association of Official Agricultural Chemists. 1 

 Where flour instead of starch is used as a filling the gluten would give 

 ammonia, of course, and wherever a tartrate powder was found to give 

 any appreciable amount of ammonia by the method, a weighed portion 

 was taken, water added, the solution filtered from the starch, and sub- 

 jected to analysis. The results were practically the same as those ob- 

 tained directly from the powder. Probably flour is not often used. In 

 the case of the alum powders, the difference that would be made by 

 flour filling was disregarded, as the amount of alum present is suffi- 

 ciently established by the percentage of aluminium oxide and sulphuric 

 acid found ; the amount of ammonia found was almost invariably low 

 in proportion to these other constituents of ammonia alum. 



ESTIMATION OF MOISTURE. 



The percentage of water of association and combination as given in the 

 analyses was obtained by difference. A number of attempts were made 

 to estimate it directly in the following way : A weighed portion of the 

 sample was placed in a U tube, which was kept immersed in boiling 

 water. At one end this tube was connected with a series of sulphuric- 

 acid wash-bottles, and at the other with weighed potash bulbs filled 

 with sulphuric acid, and beyond these with an aspirator. In this way 

 a current of dried air was drawn through the sample while it was kept 

 at 100 C., and the water drawn from it in this way was absorbed by tlio 

 sulphuric acid in the potash bulb, while the carbonic acid was drawn 



1 Fully described in Bull. No. 19, Cbem. Div. U. S. Dep't Agriculture. 



