56 REPORT — 1841. 



of other products are generated. Similar results are obtained with protochloride of 

 tin, phosphorous acid, and other powerful reducing agents. It boils at about 338° 

 Fahr., and freezes at about 21° Fahr., forming large square prisms, gradually chan- 

 ging into a mass resembling ice in appearance. The density of its vapour by calcula- 

 tion is 7'2S1 ; experimentally it was found to be 7" 101. By combustion with oxide 

 of copper, two experiments yielded the following results : — 



1. 2. 



Carbon 2230 22-23 



Hydrogen 5-48 5-33 



Arsenic 71-29 71-00 



Loss and oxygen '93 1-44 



100-00 100-00 



which numbers closely agree with the following theoretical numbers : — 



4 Carbon 23-15 



6 Hydrogen 5-67 



2 Arsenic 71-18 



100-00 

 This approximation is as great as can be expected, where the exclusion of oxygen is 

 so essential, and so difficult to be effected. 



Kakodyle thus insulated can be combined directly to form all the various substances 

 of which this series consists. By direct exposure to oxygen the oxide and acid are 

 formed. Sulphur dissolves in kakodyle, forming a solution whic?i possesses all the 

 properties of the sulphuret; and the higher degiee of sulphuration is obtained with 

 equal facility by the addition of a larger portion of sulphur. This is a solid, soluble 

 in aether, from which solution it may be obtained in beautiful crystals. An aqueous 

 solution of chlorine added to the radical occasions the immediate production of the 

 chloride of kakodyle, and most of the other compounds may be procured with nearly 

 equal facility. If kakodyle be distilled with chloride of zinc, various products of 

 different degrees of volatility are obtained, containing various proportions of arsenic ; 

 the most volatile being the least disposed to spontaneous inflammation in the air, 

 and containing the smallest amount of arsenic. By heating the vapour of any of 

 these products in a jar over quicksilver to a temperature not greatly exceeding the 

 boiling point of that metal, it undergoes decomposition, metallic arsenic is deposited, 

 and carburetted hydrogen is formed, without the smallest deposit of carbon. The 

 gaseous mixture burns with a clear bright flame, depositing a minute film of arsenic, 

 caused by traces of a volatile arsenical compound, which gives the gas the property 

 of inflaming when passed up by bubbles into a jar containing chlorine. Mixed with 

 oxygen and detonated, 1-5 vol. of gas requires 3-5 of oxygen for combustion, and 

 2-0 vols, of carbonic acid are formed. This shows it to contain 4 vols, of carbon 

 vapour and 12 vols, of hydrogen, condensed into 6 vols. Fuming sulphuric acid 

 absorbs one-third of the carburetted hydrogen, and the remaining gas, when deto- 

 nated with oxygen, gives the same results as marsh gas. It is unaffected by chlorine 

 in the dark, but in sunshine forms camphor-like crystals, exactly like those produced 

 in similar circumstances from the marsh gas. Among the products of the decompo- 

 sition of kakodyle is a remarkable substance termed by Bunsen Erythrarsin. At 

 present it can only be obtained as a secondary product, and the following method 

 yields it the purest :— About 100 grammes of oxide of kakodyle are treated with 

 strong muriatic acid ; chlorine of kakodyle is the principal product, but at the same 

 time a flocculent brick-red precipitate occurs, which remains behind aftei the chlo- 

 ride has been distilled : during the boiling it collects into darker coloured masses. 

 It is treated several times with absolute alcohol to remove the last traces of chlorine. 

 Air must be carefully excluded during the whole process, and it must ultimately be 

 dried in vacuo, as slow oxidation would otherwise occur, arsenious acid being formed. 

 The 100 grammes of oxide of kakodyle affords only 0-5 gramme of erythrarsin. Thus 

 obtained, erythrarsin forms an amorphous almost inodorous mass, of a colour between 

 dark red and steel-blue, and is easily reduced to a brick-red powder. It is insoluble 

 in alcohol, aether, water, and solution of potash. Fuming nitric acid decomposes it 

 with production of light. In weaker acid it also dissolves with decomposition. 



