54 REPORT — 1870. 



tion of the roadways. It is difficult to prove the economy resulting from the use 

 of the chlorides over a limited area ; but over large areas it is very evident. The 

 importance, in a sanitary point of view, of the use of chlorides has been clearly 

 established. The chloride of calcium decomposes the carbonate of ammonia con- 

 tained in the horse-droppings, the results being carbonate of Ume and chloride of 

 ammonium, which two results, combining with the chloride of sodium and the car- 

 bonate of lime contained in the roadway, cause the concreting effect so important 

 in the prevention of dust and the preservation of the roads. 



A. new Chlorine Process witJwut Manrjanese (luitli illustrations'). 

 By Henet Deacon. 



A heated mixtm'e of hydrocliloric 'acid gas and oxygen or air are passed over 

 heated salts of copper, lead, or manganese, or pieces of burnt clay, or similar porous 

 bodies previously soaked in solutions of the salts. Under these circumstances tlie 

 chlorine of the hydrochloric acid is set free ; and the action is so complete that, by 

 proportioning the surfaces of the salts and current of gases, the whole of the chlo- 

 rine can be liberated or all the oxygen or air absorbed. At 750° F. the reaction is 

 most active with copper salts ; lead salts require a higher temperature, and man- 

 ganese salts still higher ; and as the temperatures increase, it is believed chlorine 

 reacts on the vapour of water produced to re-form hydrochloric acid. With copper 

 salts no such re-formation occm-s. If the temperature be too high, chloride of 

 copper alwaj'S sublimes, whatever salt of copper be first employed. 



The author predicted this reaction, so far as the chloride of copper and of man- 

 ganese are concerned, from the belief that chemical forces may be united and 

 resolved as mechanical forces are, and as, he believes, is evidenced in the ordinary 

 manufactures of sulpliuric acid and of sulphuric ether by the continuous processes. 



Tlie positive proof or disproof of this theory appears only to be possible by con- 

 sidering the time occupied. If a result follows from the formation and subsequent 

 decomposition of a compound, the total time will be the time of the two processes 

 added together ; but if it be a direct result of the union of the forces, it will be the 

 time only of either process alone. This proof being at present unavailable, the 

 author relies on the test of the other proof of a correct theory, viz. its power of 

 foretelling unknown events, and claims in this instance to have shown the great 

 probability of the truth of his theory, admitting that it is not yet strictly proved. 



Note on Thermal Equivalents. — 1. Fermentation. 2. Oxides of Chlorine. 

 By James Dewar, F.B.S.E. 



On Cyanogen. By Thomas Faieley, F.C.S., Science Master at the Leeds 



Grammar School. 



I. Prqntration of Cyanogen. — The author has found the most convenient method 

 for the preparation of cyanogen to be the action of one part of pm-e potassium cy- 

 anide, dissolved in as little water as possible, on two parts of powdered copper 

 sulphate, mixed vsdth scarcely more water than sufficient to moisten and cover it. 



The operation may be performed in an ordinary bottle or flask ; and the cyanide 

 solution should be added a little at a time, as' the action is very rapid. Much 

 water prevents the action. Besides its convenience, this method gives at least 

 two 15ths of the weight of the cyanide as cyanogen. Careful experiments, made with 

 mercuric cyanide, show that it 'is very difficult to obtain more than one 15th of its 

 weight as cyanogen, i. e. only one third of the cyanogen it contains. 



n. Hydrogenation of Cyanogen. — In a former paper the author showed that when 

 cyanogen and hydrogen are passed over platinum black at 140° C, they combine. 

 He ha.9 repeated and extended these experiments, and finds that the substance ob- 

 tained by passing the gases into dilute hydrochloric acid is the chloride of an organic 

 base contaming C, II, N, CI in the exact proportions of the chloride of ethylene 

 diammouium. The chloride is soluble in absolute alcohol, and, heated with alkalies, 

 gives ofl" a liquid base. The chlorplatiuato is very soluble in water, and soluble to 



I 



