$ 



Determination of Nitrogen in Organic Compounds. 255 



hydrochloric acid of the ordinary strength, and this part of the 

 operation is done by allying the mouth to the extremity d, and 

 drawing the acid through the extremity g. 



" As means of decomposing the organic substance containing 

 nitrogen, that is to say, of oxydizing its carbon and hydrogen, we 

 make use of the hydrate of potash, or soda mixed with caustic 

 lime, in such proportions, that the mixture when exposed to a 

 strong heat will not melt, but only slightly run together. This 

 mixture has the advantage of being easily pulverized, and of not 

 attracting moisture very rapidly, and generally it is managed with 

 the same facility as the bioxide of copper or the chromate of lead. 

 We h?ve preferred latterly the mixture containing soda, in prefer- 

 ence to that with potash ; because the hydrate of soda, on account 

 of its smaller atomic weight, contains more water, and conse- 

 quently more oxydizing material than the same weight of the 

 hydrate of potash. Also the mixture of the hydrate of soda and 

 lime attracts moisture less readily than that of potash and lime ; 

 and moreover, the hydrate of soda requires but twice its weight 

 of anhydrous lime to form a mixture that will not melt at a red 

 heat. For one part of potash three of lime are necessary. The 

 easiest method of preparing it, is to slake the lime in a solution 

 of known concentration, of either of the above alkalies ; heat the 

 mixture to redness in a crucible, and rub it to a fine powder. Or 

 we may rub up quickly one of the alkalies (first melted and then 

 cooled) in a warm mortar, and then mix intimately with it anhy- 

 drous lime in the proper proportion. In this latter case, the lime 

 must be first slaked and then heated to redness as a fine powder 

 before being used. The mixture prepared in either of the above 

 ways is once more heated to redness to drive away all mixture 

 and then preserved in a well stopped phial." 



In performing an analysis, the process is as follows : 



" The burning tube, clean and dry, is half filled with the alka- 

 line mixture, and that is the measured quantity to be mixed with 

 the substance about to be analyzed, which is first dried and 

 weighed in the ordinary method. The quantity of the substance 

 employed should vary according as it contains more or less nitro- 

 gen. When rich in this element about three grains, but when 

 its quantity is quite small about six grains should be used." 



" The mixture of the weighed substance with the measured 

 quantity of the alkaline powder, is done in a porcelain mortar 



