1846.] Analysis of Soils. 237 



the copper by mixing the pulverized apocrenate with distilled 

 water, and passing sulphydric acid gas through the mixture until 

 all the copper is separated as a sulphuret, and then filter and 

 evaporate the apocrenic acid to dryness; or we may burn off the 

 apocrenic acid and weigh the oxide of copper obtained, and by 

 difference in weight determine the proportion of apocrenic acid. 

 The same method may be pursued in the analysis of the crenate of 

 copper. The crenate is however much more easily decomposed 

 by sulphydric acid gas, and the crenic acid if collected and dried 

 off in a shallow glass vessel, separates readily from the glass in 

 the form of a thin honey -yellow scale. 



Humate of lead is decomposed by sulphydric acid gas, and sul- 

 phuret of lead separates readily. Filter the solution, and evapo- 

 rate to dryness, i he composition of humate of lead may be 

 learned also by converting the oxide of lead into a sulphate, and 

 calculating the quantity of oxide of lead from the sulphate. 

 When these organic acids are required in their pure state for 

 combustion with oxide of copper, it is necessary to form these 

 salts a second time, in order to avoid admixture. The analysis 

 by oxide of copper determines the proportions of oxygen, hydro- 

 gen and carbon. The nitrogen must be determined by a separate 

 operation, a mixture of lime and soda being used, and the nitro- 

 gen being converted into ammonia, which is to be precipitated 

 by chloroplatinic acid, and calculated from the w^eight of the 

 chloroplatinate of ammonia produced. 



The apocrenic, crenic and humic acids having been analyzed, 

 it is unnecessary to repeat the operation, it being only necessary 

 to obtain the w^ell known combinations with metallic oxides, as 

 above described. When a new organic substance is discovered, 

 it is necessary to make an ultimate analysis of it, in order to fix 

 its composition and to classify it among organic matters that have 

 been analyzed. 



Apocrenic acid consists, according to Hermann, of 

 Carbon, - - - 62.57 

 Hydrogen, - _ _ 4.8O 

 Nitrogen, - - - 15.00 

 Oxygen, - . - 17.53 



