M. Casselmann on the Oxychlorides. 189 



PCP, corresponding to the oxychloride, PO^ CF, is known, the 

 latter substance was chiefly used in the research. 



He expected that by acting on oxychloride of phosphorus with 

 substances which,, under certain circumstances, readily exchange 

 chlorine for oxygen, the pentachloride of phosphorus would have 

 been obtained. In this direction the comportment of the chlo- 

 rides of aluminium, magnesium, and zinc, and of the bichloride 

 of tin, was investigated, but without the expected results. On 

 the other hand, interesting compounds of oxychloride of phos- 

 phorus with these chlorides were obtained, which Casselmann 

 describes at length. 



The compound of oxychloride of phosphorus with bichloride 

 of tin, 2Sn CP + PO^ Cl^, he had previously described. It forms 

 large colourless crystals, and when pure, distils unchanged. On 

 account of the readiness with which this compound, and indeed 

 all the compounds of this nature, attract moisture, they are ex- 

 tremely difficult to get quite pure ; their preparation is effected 

 in an apparatus by which the access of moisture is prevented. 



Berzelius viewed oxychloride of phosphorus as a compound of 

 phosphoric acid and pentachloride of phosphorus, 



5P02CF=2PO^ + 3PCP. 



Such a compound would give with bichloride of tin, phosphate of 

 tin, and the compound of pentachloride of phosphorus with bi- 

 chloride of tin (PCP + 2SnCP), previously described by Cassel- 

 mann. But as the compound of oxychloride of phosphorus with 

 bichloride of tin may be volatilized, no phosphate of tin can be 

 contained in it, and Berzelius's view is hence not correct. 



Oxychloride of phosphorus exhibits a strong tendency to com- 

 bine with bichloride of tin. When brought into contact with 

 the compound of bichloride of tin and bichloride of sulphur, 

 SnCF + 2SCP, the compound of oxychloride of phosphorus with 

 bichloride of tin is obtained, bichloride of sulphur being set free. 



When chloride of aluminium is mixed with oxychloride of 

 phosphorus in a sealed tube, a white mass is obtained, which on 

 heating, dissolves in the excess of oxychloride of phosphorus ; 

 and on cooling, the compound of oxychloride of phosphorus with 

 chloride of aluminium is deposited in clear colourless needles. 

 Its formula is AP CF + PO^ CF. 



With chloride of magnesium a compound is obtained which 

 has the formula 2MgCl + PO^ CF. 



With chloride of tin a compound crystallizing in rhombic plates 

 is obtained. 



With metallic oxides the oxychlorideof phosphorus decomposes, 

 so that a metallic phosphate and a metallic chloride are formed. 

 It cannot therefore be considered as phosphoric acid in which 



