412 THE CANADIAN NATURALIST. [Vol. ix. 



certainty what proportion of flour is necessary for this purpose, 

 I should think, however, that 10 per cent, would amply suffice, 

 although a leading manufacturer tells me that 25 or 30 per cent, 

 is necessary. I should certainly consider this quantity much 

 greater than is absolutely necessary, for baking powders are not 

 generally kept for any great length of time, and further I have 

 found upon careful examination that those powders containing 

 10 per cent, or less of flour had not lost any of the carbonic 

 acid they originally obtained ; of course I cannot say how long 

 they had been made before examined. 



The presence of a small quantity of lime, say 2 or 3 per cent., 

 cannot be regarded as injuring the powder. It is a well-known 

 fact that bakers frequently use lime-water to produce in their 

 bread "whiteness, softness, and capacity of retaining moisture." 

 The lime removes all acidity from the dough, and supplies an 

 ingredient needed in the structure of the bones but which is de- 

 ficient in the flour. It is therefore advantageous rather than 

 otherwise that a baking powder should contain a small percentage 

 of pure lime. 



The second class contain those powders which depart from 

 our type in having alum substituted in part or entirely for 

 cream of tartar. One of this class contained alum 4*7, flour 

 47-59, and yielded carbonic dioxide only 8-42. Another had 

 alum 1-89, flour 34*00, and yielded carbonic dioxide 10-4. In 

 these two, alum only partially replaced the cream of tartar, but 

 in many powders it is the sole acid substance. One of this group 

 contained alnm 17-032, flour 67*25, and yielded 11 per cent, of 

 carbonic dioxide. , 



The second class of powders is remarkable for several reasons^ 

 First, the small percentage of gas produced ; secondly, from the 

 fact that alum iu part or entirely replaces cream of tartar ; and 

 lastly, because of the large quantity of flour they contain. 



Cream of tartar costs about 28 or 30 cents per lb., whilst 

 alum can be purchased for less than 2 cents per lb. The former 

 must be used in much larger quantity than alum to act upon the 

 same quantity of soda in order to deprive it of all its carbonic 

 dioxide. There is therefore an inducement, so strong that many 

 cannot withstand it, to use alum as a substitute for cream of 

 tartar in the manufacture of baking powder. 



Now, is this alum to be regarded as an adulterant ? Is it 

 injurious to those who use it in these powders ? To both of 



