BAKING POWDERS. 599 



not so pure in this respect. Chemists will readily understand the im- 

 possibility of giving the proportions of the various forms of lime phos- 

 phates contained in such a substance. As gi veil in the tables the relative 

 acidity is shown, though of course the phosphoric acid does not occur as 

 free acid. 



Both the alum and the lime phosphate contain large percentages of 

 water, hygroscopic moisture in the latter, and crystallization water in 

 the former, so that the per cents, of the " anhydrous " salts given are 

 always lower than the proportions of the hydrated salts originally used 

 in compounding the powder. Nearly half the weight of the alum is 

 crystallization water, some part of which is probably driven off in some 

 cases when it is used for baking-powder purposes, but there are no 

 means of ascertaining how much, and of course the moisture in the acid 

 phosphate would vary in different samples, so there is no possible way 

 of approximating the amounts of the hydrated substances, as they were 

 originally used. 



Ammonia bicarbonate is another substance of indefinite composition. 

 As given in the tables it has been calculated from the ammonia found, 

 upon the assumed composition given it in the U. S. Pharmacopoeia, viz, 

 NH 4 HCO 3 .NH 4 NH 2 OO 2 . 



In case ammonia carbonate were present in any of the powders con- 

 taining ammonia alum, I know of no way of estimating the amount or 

 even the fact of its presence in the small quantities used. 



The percentage of " available carbonic acid " is placed first in the 

 tables as constituting the most important indication of the efficiency of 

 the sample as an aerating agent. 



TABTEATE POWDERS. 



5503. Boya Baking- Powder. 

 [Manufactured by The Koyal Baking-Powder Company, New York 1 



Available carbonic acid percent.. 12*74 



Cubic inches per ounce of powder at 212 F 153.0 



Leavening gas (available CO 2 -j- NH 3 ) per cent.. 13. 06 



Cubic inches per ounce of powder at 212 F 160.6 



PERCENTAGE COMPOSITION. 



Total carbonic acid, CO 2 12.92 



Sodium oxide, Na 2 O 10.30 



Potassium oxide, K 2 O 12.02 



Calcium oxide, CaO. .13 



Ammonia, NH 3 .32 



Tartaric acid, CJLAi 37.46 



Sulphuric acid, SO 3 .25 



Starch 16.34 



Water of combination and association by difference 10. 26 



100. 00 



