510 [March 26, 



After diffusion for an hour at about 520 C., the residue was 



composed of 



60 Mono-hydrated sulphuric acid. 



40 Sulphuric anhydride. 



100 



In another experiment we took an acid containing 

 99 Mono-hydrate. 

 1 Water. 



100 



and after diffusion for a shorter time at 445 C. found the residue to 

 consist of 



75 Mono-hydrate. 



25 Anhydride. 



100 



In both cases the residues after diffusion fumed strongly on 

 exposure to the air, and consisted partly of crystals and partly of 

 liquid. 



The substance next submitted to diffusion was pentachloride of 

 phosphorus, which is decomposed by heat into terchloride and free 

 chlorine. 



The pentachloride which we used gave no reaction with iodide of 

 potassium and starch, and therefore contained no free chlorine ; it 

 gave no precipitate with corrosive sublimate, and therefore contained 

 no terchloride of phosphorus. An analysis of it gave 

 Percentage of chlorine =84* 6 7 

 The formula requires ... 85*13 



In one experiment we diffused into carbonic acid gas* for three- 

 quarters of an hour at about 300 C., and afterwards dissolved the 

 contents of the lower flask in water, and precipitated with corrosive 

 sublimate, with the addition of a little hydrochloric acid. *0175 

 gramme of calomel was obtained. In another experiment (also 

 into carbonic acid) the time of diffusion was two hours, temperature 

 300 C., quantity of calomel obtained -0285 gramme. 



These two results leave no doubt as to the existence of terchloride 



* If pentachloride of phosphorus be diffused into air, the residual terchloride 

 combines with oxygen to form oxychloride of phosphorus, which does not reduce 

 corrosive sublimate. 



