BAKING POWDERS. 619 



PROBABLE PERCENTAGE COMBINATION. 



Sodium bicarbonate, NaHCO 3 18.75 



(Residual sodium oxide, Na^O) 5.37 



Arumouia alum, anhydrous : 



A] 2 (SO 4 ) 3 11-12 



(NH 4 ),SO 4 a. 59 



14.71 



Calcium sulphate, CaSO 4 5. 58 



Acid phosphate of lime, anhydrous: 



Ca 3 (PO 4 ).;! 4.19 



H 3 PO 4 2.51 



6. 70 



Starch 40.19 



Water of association (phosphate) and crystallization (aluui) 8.70 



100. 00 



These analyses agree pretty closely, in a general way, with those made 

 by Professors Weber and Cornwall, so far as their determinations go. 

 ^Professor Cornwall's figures for carbonic acid are uniformly higher than 

 mine, his method giving rather the total than the available per cent, of 

 gas. It is evident that the determination of available carbonic acid 

 made upon saTnples obtained in retail stores would vary more or less, 

 according to the time that had elapsed since the sample was first put up. 

 This is well shown by Professor Cornwall's determinations (page 58G), 

 made upon samples of the same brand of powder purchased at different 

 times. It would manifestly be unjust, therefore, to decid3 arbitrarily 

 that the relative values of the different brands were in the exact rank 

 indicated by the results given in this determination. The best results 

 in all the different investigations, however, are given by the tartrate 

 and phosphate powders, the alum, and the alum and phosphate pow- 

 ders giving almost uniformly low percentages of carbonic acid. (There 

 are several exceptions, however, notably Professor Cornwall's No. 36, 

 "One Spoon" giving 16.77 per cent. 1 This shows the possibilities of 

 an alum powder as regards its carbonic-acid strength.) 



Professor Cornwall's average for twenty samples of alum and phos- 

 phate powders (no straight alum powders included) is 8.97 per cent. ; for 

 eight samples of tartrate powders, 11.60. Professor Weber's average 

 for nineteen samples of alum powders is 7.58 per cent, ; for eight samples 

 of tartrate powders, 11.20 per cent. My average for twenty samples of 

 both alum, and alum and phosphate powders is 8 percent.; for eight 

 samples of tartrate powders, 10.10 per cent. The only straight phos- 

 phate powders sold seem to be the various preparations made by the 

 Eumford Chemical Works, and the "Wheat" powder; at least these 

 ire all obtained by any of the investigators. The carbonic acid strength 

 of the former is uniformly good, slightly higher than the tartrate pow- 



1 Weber obtained only 5.75 per cent, from a powder with this brand in his investi- 

 gation. Page . 



5360 pt, 5 5 



