BAKING POWDERS. 589 



ANALYSES BY U. S. DEPARTMENT OF AGRICULTURE. 



The samples for the following analyses were all purchased at retail 

 stores in Washington, D. C., by an agent of the Department, no intima- 

 tion being given to the seller of the purpose for which they were in- 

 tended. The city was pretty thoroughly gone over, and the samples 

 probably include about all the different brands sold. 



METHODS OF ANALYSIS. 



Following are detailed descriptions of the methods followed in the 

 analyses made in this laboratory. In many of the estimations different 

 methods were tried, and the one which gave the best results and was 

 found to be most cou\ 7 euieut was chosen. 



GENERAL EXAMINATION OF SAMPLES. 



The qualitative and general examination is described in the extract 

 from Professor Cornwall's report above, and it is not necessary to go 

 into it in detail again, as the methods were similar, generally speaking. 

 The qualitative examination and assignment of a sample to one of the 

 classes indicated presents no special difficulties. If it is desired to 

 know the character of the filling used, it is readily ascertained by a 

 microscopical examination ; but this is rather an unimportant matter. 

 A determination of the alkalimetry of the watery solution of the powder 

 is useful as showing whether any great excess of alkali had been used. 



ESTIMATION OF CAEBONIC ACID. 



This is one of the most important estimations, as it determines the 

 strength of the powder. It was made by absorption with soda lime, 

 and a form of apparatus was used that has served for some time in this 

 laboratory for the determination of carbonic acid. This apparatus has 

 recently been somewhat modified and greatly improved in com pact ness 

 by Mr. A. E. Knorr. It is shown in the accompanying figure. Follow- 

 ing is Mr. Knorr's description : l 



The apparatus proper, as represented by the cut, consists of a flask A in which the 

 carbon dioxide is sstfree. A condenser D is ground into the neck of this flask and 

 condenses the steam formed when the liquid in A is boiled in order to secure complete 

 expulsion of the gas. The reservoir B contains the acid required for the operation, 

 and has a soda-lime guard C ground into it to retain the carbonic acid of the air, a 

 constant current of which is aspirated through G during the whole operation. The 

 stem of the reservoir is ground into the condenser, or it may be conveniently blown 

 into one piece with it. The carbonic acid is dried in E and finally absorbed in the 

 weighed potash bulb F. 



Two determinations of carbonic acid were made on each sample one 

 by the addition of acid to determine the total amount of carbonate pres- 



Jour. Aualyt. Cbern,, 3, 162. 



