346 Dr. Gladstone on the Compounds of the 



It is also well known, that if the combination between phos- 

 phorus and the halogen be made by means of a metallic salt 

 that yields up its electro-negative element readily, or in 

 other words, if phosphorus be distilled with the chloride, bro- 

 mide, or iodide of mercury, it is the ter-compound that results. 

 In this manner also Davy produced a ter-fluoride. Canedella* 

 states that if cyanide of mercury and phosphorus be heated 

 together, combination ensues, frequently with explosive vio- 

 lence, and a sublimate is formed resolvable by water into 

 phosphorous and hydrocyanic acids. On repeating his ex- 

 periment I did obtain a sort of explosion, and a minute quan- 

 tity of a substance which answered somewhat to the description 

 given. A subsequent attempt, however, was quite unsuc- 

 cessful. The uncertainty attending the preparation, together 

 with the high probability that poisonous exhalations would 

 arise from such cyanides when exposed to the air, rendered 

 me disinclined to pursue the investigation further. 



In order to prepare one of these ter-compounds by means 

 of a metallic salt, it is not necessary that* the salt should be 

 capable of decomposition by heat alone. I have prepared ter- 

 chloride of phosphorus by making use of the chlorides of 

 iron and copper ; and doubdess other metallic chlorides might 

 be substituted. Chloride of lead, however, I found not to be 

 decomposed by phosphorus. 



The comparative weakness with which the two additional 

 atoms of the pentachloride of phosphorus are held in combina- 

 tion, is evident from the ease with which compounds are ob- 

 tained, where these two atoms of chlorine are substituted by 

 sulphur and oxygen, as already made known by Serullas and 

 Wurtz; but the readiness with which the penta-corapounds 

 are reduced to the ter-compounds has never, I think, been 

 pointed out. If the chloride, bromide, or iodide of phos- 

 phorus, containing five atoms of the halogen, be heated in con- 

 tact with fresh phosphorus, chemical action is instituted, and 

 the whole is reduced to the compound containing three atoms. 

 With the bromide the application of extraneous heat is quite 

 unnecessary: with the iodide, the reduction will proceed even 

 to the formation of a compound containing a much smaller 

 amount of iodine, but of a totally different character to the 

 bodies now under consideration. Upon this may be founded 

 a good method for obtaining the terchloride and terbromide, 

 as their freedom from admixture with the higher combination 

 can then be depended upon : sufficient phosphorus must be 

 employed to reduce the whole, and the liquid may be distilled 

 of perfect purity. Similarly, it has been heretofore observed, 

 * Annul, der Pharm., xviii, 70. 



