Prof. Bunsen on Cacodyl Compounds containing Platimm. 399 



To estimate the quantity of the bromine, 0-7145 gramme 

 was dissolved in water, precipitated by nitrate of silver, and 

 boiled some time with nitric acid, by which 0-452 bromide of sil- 

 ver was obtained. This researchffives the following numbers: — 



3744-76 100-00 

 To determine the proportion of water in the substance, 

 1-2534 gramme was dried at 100° C. and then heated in an 

 oil -bath at 200°, till no more weight was lost. The loss was 

 0-040, which is equal to 3-200 per cent. It will be seen that 

 this compound, like that of chlorine, contains 1 atom of water. 

 The formula for the hydrous and anhydrous compounds 

 respectively are 



Pt02C4H7As2Br, 

 PtO C4H6As2Br. 

 In this compound also the water can be replaced by ammonia. 



Iodide of Cacoplatyl. 



The yellow precipitate which iodide of potassium forms 

 with chloride of cacoplatyl is this iodide. By mixing the two 

 solutions, boiling hot and tolerably dilute, the iodide separates 

 in the form of glistening scales of a silky lustre, resembling 

 the iodide of lead. It possesses nearly the same degree of 

 solubility in water as the last-named substance. 



The iodide differs from the other compounds of cacoplatyl 

 in losing its whole water at 100° C. ; it becomes then of a 

 brown violet colour without melting. The brown crystals dis- 

 solve in water, forming a yellow solution, which deposits cry- 

 stals again on cooling. 



This compound also is inodorous, and may be submitted 

 to a high temperature without decomposition. It is injured 

 at 260° C, wlien the compound melts and becomes black, 

 giving off dark vapours smelling like alcarsin, and, lastly, 

 burns like tinder, leaving the arseniuret of platinum. For the 

 analysis of this substance, it was dried and burned with oxide 



