620 FOODS AND FOOD ADULTERANTS. 



ders ; the latter is a peculiar preparation, made up without any filling 

 whatever, and gives a very low percentage of carbonic acid, except in 

 one of Professor Cornwall's samples, which seems to have been obtained 

 quite fresh. 



FILLING. 



It is evident that of several powders made up of the same materials, 

 the one which contains the smallest proportion of inert matter or filling, 

 other things being equal, will have the best carbonic-acid efficiency or 

 " strength." On the other hand, if the amount used is too small for the 

 proper preservation of the sample, it will deteriorate rapidly, and per- 

 haps will show less strength after keeping a short time than other 

 powders with a somewhat larger amount of filling. It becomes a ques- 

 tion, therefore, as to the minimum limit of the amount of filling that is 

 consistent with good keeping qualities. Professor Prescott 1 says on 

 this point : 



From 13 to 18 per cent, of starch is not too much for the permanence of a cream of 

 tartar baking-powder, but filling beyond 20 per cent, must be held an unquestionable 

 dilution. 



In my samples, the average per cent, of starch in the bitartrate pow- 

 ders was 14.04 ; the highest was 24.57 per cent., and the lowest 5.32 

 per cent. The latter sample evidently did not contain enough, fcr it 

 had a much lower carbonic-acid strength than most of those that had 

 more filling. The bitartrate powder containing the maximum of fill- 

 ing, No. 5527, contained also the lowest per cent, of available car- 

 bonic acid. The powders made up with free tartaric acid contained 

 much more filling, this being doubtless necessitated by the more hy- 

 groscopic character of the free acid. They contain, respectively, 40.05 

 and 45.63 per cent, of starch, and 9.53 and 4.98 per cent, of available 

 carbonic-acid. Of the phosphate powders No. 5508 contains rather a 

 large amount of filling, 26.41 per cent., while No. 5506 contains none 

 at all, evidently to its detriment, as previously noted. ^ Even the acid 

 part of No. 5509 contains 20.81 per cent, of starch, although it is kept 

 separate from the alkali. It is in the alum, and the alum and phosphate 

 powders, however, that the highest percentages of filling are found. 

 The average of all is 40.76 per cent, of starch, the maximum 52.29 per 

 cent., the minimum, 3J.54 per cent. Here we find the cause for the'low 

 per cents, of available carbonic acid in these powders, which should, 

 theoretically, afford a higher carbonic-acid strength than any of the 

 other classes. Whether a large amount of filling is more necessary 

 where alum is used to prevent deterioration, whether it is added simply 

 as a diluent, so that the amount of alum taken into the starch will be less 

 apt to produce an injurious effect, or whether it is added to cheapen the 

 powder, I can not say. The first hypothesis seems the most probable, 



1 Organic Analyses, r>00. 



