INDUSTRIAL PROGRESS DURING THE YEAR 1874. xlvii 



of the Ruiz thermal spring, which contains 3.664 grammes of 

 pure sulphuric acid in one litre. As the former river delivers 

 34,785 cubic meters of water daily, it follows that it carries to 

 the sea every day 46,8*73 kilogrammes of sulphuric and 42,150 

 kilogrammes of hydrochloric acid; and every year seventeen 

 millions of kilogrammes of the former and fifteen millions of 

 kilogrammes of the latter. He believes that the simultaneous 

 presence of chlorides and sulphates in the rock explains the 

 production of hydrochloric, of sulphurous, and, under certain 

 conditions of temperature, of sulphuric acid in the emana- 

 tions from the volcanic craters and fumerolles; and accounts 

 consequently for the occurrence of these acids free in the 

 thermal springs of the equatorial Cordilleras. Rammelsberg 

 has succeeded in establishing the isomorphism of selenium 

 and sulphur. He finds that a mixture of one atom of selenium 

 to four atoms of sulphur takes the form of the latter. The 

 noteworthy fact, in regard to selenium, that its electrical re- 

 sistance is enormously diminished by the action of light, the 

 least resistance being observed in the extreme red rays a 

 phenomenon first observed by Lieutenant Sale, R. E. has 

 been confirmed by the Earl of Rosse, who obtained in some 

 cases a diminution of 38 per cent. This decrease is approxi- 

 mately as the square root of the luminous intensity. 



Carius, as the result of his investigations, concludes that, in 

 nature, nitrification takes place, (A) from free nitrogen by (l) 

 electrical discharges in the air, and (2) by oxidation in the air 

 of other bodies; and (B) from the oxidation of ammonia (l) 

 by electrical discharges, (2) by the presence of the so-called 

 alkaline substances, and (3) by ozone. Berthelot suggests the 

 preparation of nitric oxide (the anhydrous nitric acid of some 

 chemists) by the action of phosphoric oxide upon the strong 

 nitric acid. The process goes on quietly, the nitric oxide 

 crystallizing in large crystals on the walls of the receiver. 

 The same industrious chemist has investigated the heat of 

 formation of the oxides of nitrogen ; with reference to nitro- 

 gen dioxide, he says : " Such an aptitude for slow and mul- 

 tiple decompositions characterizes compounds which are but 

 imperfectly stable, and which are formed with absorption of 

 heat. Nitrogen dioxide, in this respect, is comparable to 

 cyanogen and acetylene ; all these compounds possess an 

 aptitude for entering into chemical combination, a sort of 



