512 Dr. H. E. Armstrong on Acids of the Sulphur Series. [June 16, 



and S0 3 , S0 2 , and CL are the final products obtained on heating, 4*96 is 

 the theoretical number. 



The experimental number, however, lies between the two latter, and it is 

 therefore to be supposed that already, at a temperature of 200°, the disso- 

 ciation was almost complete. 



I intend making a series of determinations at varying temperatures and 

 pressures, especially as H. Rose and Rosenstiehl have obtained numbers 

 very different from mine; the former gives 8'96 as the mean of 5 con- 

 cordant experiments all made at about 200°, and the latter 7*52, the tem- 

 perature at which the determination was made not being given in this case. 



The action of phosphoric chloride on the chloride is somewhat remark- 

 able. On bringing the two together a violent action takes place, and sul- 

 phurous anhydride and chlorine escape ; after adding slightly more than 

 1 equivalent of the chloride and 1 equivalent phosphoric chloride, and 

 warming a short time, the latter had entirely disappeared. On distilling 

 but little passed over below 130°, the greatest portion between 130° and 

 140°, and from 140 3 to 150° about one-third of the whole. Under all cir- 

 cumstances the formation of phosphoric oxychloride was to be expected, 

 and it was therefore remarkable that so little had distilled over within the 

 limits of its boiling-point. The analysis of the three fractions, however, 

 has shown that they are all mixtures of POCl 3 and S 2 0 5 C1., in varying pro- 

 portions. 



From fraction 1 (130°),— 



•1655 grm. gave '409 grm. AgCl =6 1*1 CI. 

 •4027 grm. gave -1395 grm. BaS0 4 = 4*75 S. 

 •165 grm. gave '0777 grm. Mg a P a 0 7 = 13*15 P. 



The amount of phosphorus shown by analysis corresponds to 65*1 

 POCI3 ; but the amount of chlorine remaining after deduction of that re- 

 quired by the phosphorus and the sulphur are not in the proportion re- 

 quired either by sulphuric chloride or by pyrosulphuric chloride : it is 

 therefore probable that a mixture of both is present. 



The second fraction still contained 20*8 POCl 3 . 

 The third „ „ 12 5 POCl 3 . 



The decomposition is accordingly expressed by the equation — 



S 2 0 5 C1 2 + PCL = POCI3 + 2SO s + Cl 4 . 



Sulphuric chloride, which it at first seemed probable would be the sole 

 product beside phosphoric oxychloride, — 



S0 o Cl 



O ' + PC1 5 = POCI3 + 2S0 2 C! 2 , 

 S0 2 C1 



has, if at all, only been formed in very small quantity, it seems. 



As to the constitution of the bodv S 2 0 5 Cl a , all seems to speak for its 



