McClenahan — Hydrous Thallic Chloride. 107 



tion of the salt was transferred to a crucible and a few drops 

 of sulphuric acid added. This was evaporated and the tem- 

 perature was raised to approximately 200° C. The crucible 

 was cooled in a desiccator and weighed, the weight of the 

 residue was taken to be the acid thallous sulphate. The cru- 

 cible was again heated and the temperature was raised to that 

 of dull redness. After a suitable period of cooling it was 

 again weighed, and the weight of the residue reckoned as the 

 normal thallous sulphate. 



Composition of the Salt. 



Preparation I. 



Found. Theory for TlCl 3 -4H a O. 



Thallium.. _ 53*74 53*36 



Chlorine 27-81 27'80 



Water (by difference) 18-45 18 84 



100-00 100-00 



Weighed portions of this salt were transferred to weighed 

 porcelain boats which were placed in combustion tubes passing 

 through a water bath after the fashion of boiler tubes. A 

 slow current of dry air was sent through the tubes kept at 

 100°. At the end of an hour the boat was removed and 

 weighed. The residue in the boat was dissolved in water con- 

 taining nitric acid and the chlorine estimated by precipitation 

 and weighing as silver chloride. The calculated composition 

 of the salt is given below. 



Dehydration of TlCl^H^O at 100°, 



in one hour. 



Weight of 



Chlorine in 



Chlorine Loss of 



salt taken. 



Loss. Per cent. residue. 



in Chlorine 



grms. 



grms. loss. grm. 



residue. Per cent 



0-1572 



0-0282 17-94 0'0430 



27-36 -45 



0-1615 



0-0298 18-45 00447 



27-68 -13 



0-2252 



00402 17*85 0-0620 



27-55 '26 



0-2221 



0*0396 17-83 0*0614 



27-65 -16 



0-1343 



0-0237 17*65 0-0371 



27-63 -18 



0-1719 



0-0308 17-92 0-0473 



27*51 -30 



Obviously the hydrolytic decomposition during the process 

 of dehydration at 100° is very small in the case of the hydrous 

 thallium chloride T1C1 3 -4H 2 0. By the passage of dry' air at 

 100° over the salt for an hour, nearly anhydrous thallic chloride 

 was obtained, with small loss of chlorine, averaging about 1 

 per cent of the entire amount in the original salt. The anhy- 

 drous residue was crystalline and sparkling in the sunlight, but 

 highly hygroscopic. 



