M. Ullgren on the Determination of Nitrogen in Iron* 523 



tabling potash prepared as described above. The difference 

 between the weight of this after an experiment and before, gives 

 the weight of carbonic acid produced by the oxidation of the 

 carbon. 



With some kinds of carbon perfect oxidation is very slowly 

 effected; in such cases it is better first to separate all carbon 

 with neutral sulphate of copper, and then to oxidize the residue, 

 which consists of carbon and copper with chromic and sulphuric 

 acids. The author has found that the carbon which is contained 

 in chemical union with iron, as in white cast iron, is very diffi- 

 cult to oxidize. To this question, as well as to the examination 

 of the carbon in steel and in wrought iron, the author intends to 

 return. With respect to the quantities used, there must in 

 general be sixteen parts by weight of chromic acid for each part 

 of the carbonaceous substance to be oxidized, and for each 

 gramme of chromic acid 1*5 cubic centim. of strong sulphuric 

 acid should be used. Water should in most cases be added, in 

 the proportion of 2 cubic centims. to 3 or 4 cubic centims. of 

 sulphuric acid. 



Prom recent experiments which have established the presence 

 of nitrogen in cast iron, steel, and wrought iron, it appears that 

 it is present in two conditions : in one case it is liberated as 

 ammonia when iron is dissolved in hydrochloric acid, inas- 

 much as the nitrogen unites with hydrogen in statu nascenti; 

 and in the other it is left in the carbonaceous mass which remains 

 when iron is dissolved in hydrochloric acid, or when it is heated 

 with sulphide of mercury. It is very probable that the presence 

 of nitrogen greatly affects different qualities of iron, and an easy 

 and certain means of determining its presence is a desideratum. 

 To supply this, Ullgren has undertaken a research the results of 

 which he has published*. 



When iron is dissolved in hydrochloric acid, a certain quantity 

 of the ammonia formed escapes along with the vapours. The 

 quantity which thus escapes depends on the quantity and con- 

 centration of the acid ; in all cases where the nitrogen is to be 

 determined by dissolving iron in HC1, the ammonia which escapes 

 must be separately collected and taken into account. The solu- 

 tion in hydrochloric acid may, however, be avoided, and the 

 ammonia determined in one solution by dissolviug the iron in 

 solution of neutral chloride of copper. In one case two grammes 

 of cast iron were treated with a solution of ten grammes sulphate 

 of copper and five of chloride of sodium ; when the solution was 

 effected, the liquid was distilled with caustic lime and the am- 



* Liebig's Annalen, October 1862. 



