XXVI. METHODS FOR THE ANALYSIS OF BAKING POWDER AND 

 BAKING CHEMICALS. PROVISIONAL. 



All the processes hereafter described, except determination of acidity, may be 

 employed in the analysis of baking powders, and all the processes, except deter- 

 mination of carbonic acid, in the analysis of cream of tartar and its substitutes. 

 The sample under examination is entirely removed from the package, carefully 

 mixed, and passed through a sieve without grinding. 



1. Total Carbon Dioxid. 



Make the determination by the absorption method, employing any apparatus 

 which gives accurate results when checked with pure calcite. Whatever 

 apparatus is chosen, the tubes and materials used for absorbing and drying the 

 carbon dioxid may be varied according to the preference of the analyst. 

 According to the amount of absorbent employed vary the weight of sodium or 

 calcium carbonate from 0.25 to 1 gram, and use about twice as much baking 

 powder. The corrections for temperature and pressure given with the Heiden- 

 hain apparatus may ordinarily be disregarded. 



(a) METHOD USING KNORB'S APPARATUS. 



(1) DESCRIPTION OF APPARATUS. 



This apparatus (fig. 9) has only ground-glass joints, and may be quickly made 

 ready for use or taken to pieces and packed away. On the other hand, it is 

 nflexible and must be carefully handled, and has the additional disadvantage 

 that broken parts can not readily be replaced. Therefore it is of more value for 

 occasional determinations than for a .long series.** 



(2) PREPARATION OF REAGENTS. 



(1) The potassium hydroxid solution usually employed for absorbing carbon 

 lioxid has a specific gravity of about 1.27. Many analysts, however, prefer a 

 solution having a specific gravity of about 1.55. 



(2) The calcium chlorid and soda lime employed should be finely granulated 

 and freed from dust with a sieve. 



(3) DETERMINATION. 



Place some of the baking powder in a perfectly dry distilling flask. Close 

 the flask with a stopper carrying the tube connecting with the absorption 

 apparatus and also with the funnel tube. Weigh the tubes in which the carbon 



The small calcium chlorid tube shown in the cut attached to the potash bulb F is 

 usually replaced by a second Liebig bulb with sulphuric acid. Better results are obtained 

 if the same drying tubes are used before and after the potash bulb. Many analysts prefer 

 to replace the bulb F and attached calcium chlorid tube by two U-tubes filled with sifted 

 soda lime. When the second tube shows a material increase in weight it is placed first, 

 nd the first tube refilled and placed in the second position. 



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