252 MAINE AGRICULTURAT, EXPElRIMENT STATION. I906. 



used. The residues of the phosphate-ahim powders differ some- 

 what from those of either ahim or phosphate powders and vary 

 with the proportion of the different acid constituents used. 

 When the ingredients are properly proportioned in the baking 

 powder, neither alum or alum phosphate powders leave any 

 considerable amount of alum in the resulting bread or cake. 



There is a great dispute as to which of these different residues 

 are the least objectionable. The food law of this State does not 

 attempt to in any way answer the question as to which is best. 

 They are all put on the same footing of correctly stating the 

 source of the acid constituent. A baking powder is adulterated 

 under the law only when the label does not truthfully name the 

 kind of acid salt it contains ; when it is falsely labeled in any 

 particular ; or when it contains useless, inert foreign matter, 

 mineral or otherwise. 



The per cent of available carbonic acid gas furnished by the 

 different classes of baking powders is, according to Wiley,* as 

 follows : 



Cream of tartar baking powder^ 12 per cent available carbonic 

 acid gas. 



Phosphate baking powder, 13.0 per cent available carbonic 

 acid gas. 



Alum baking powder, 8 . i per cent available carbonic acid 

 gas. 



Phosphate-alum powder, 10.4 per cent available carbonic gas. 



The alum powders would require a half more than the tartrate 

 or phosphate powders to produce the same leavening effect. 

 There are however very few straight alum powders on the 

 market. Because of the greater leavening effect of the mixed 

 powders and the supposed less harmful residues, nearly all the 

 alum now used is in the phosphate-alum powders. 



The samples here collected and reported upon have not been 

 tested for strength, but merely for correctness of labeling. 

 Many of the less common brands were found by correspond- 

 ence with the manufacturers to be three or more years old. 

 Naturally such powders would not be nearly as effective leaven- 

 ing agents as when they were fresher. 



A description of the brands collected, the cost of the powders, 

 and comments follow. 



*The flgnies are quotefl from Bui. 13 of Div. of Chemistiy. U. S. Dept. of Agr. 



