*244 E. NjcJdes on Amorphous Phosphorus, 



Art. XXL — On the purification of Amorphous Phosphorus ; by 

 M. Ernest Nickles 



It is known that the phosphorus not spontaneously inflamma- 

 ble or amorphous phosphorus (called also red or allotropic phos- 

 phorus), is obtained by heating common phosphorus for some 

 time at a temperature between 230° and 250° C, in an atmosphere 

 of nitrogen, hydrogen, or other gas free from oxygen. But how- 

 ever long the treatment be continued, a portion of the phospho- 

 rus always escapes the change and must be removed, if we 

 would not compromise the essential qualities of the amorphous 

 phosphorus, its innocuity and its unalterability in the air. The 

 mode of purifying it proposed by Sch rotter, its discoverer, is 

 very inconvenient. It is based on the use of sulphuret of carbon 

 which dissolves ordinary phosphorus without acting on the other. 

 The process theoretically seems to be a simple one ; but it is in 

 practice attended with much trouble and danger ; for the wash- 

 ings are not only interminable and require a large quantity of 

 the sulphuret of carbon, but besides this, the chances of inflam- 

 ing it increase rapidly with the proportions of phosphorus 

 under treatment. M. Sch rotter has from the first sought to re- 

 move the danger by recommending that the filter be kept full 

 of the sulphuret so that the ordinary phosphorus which deposits 

 on the borders of the filter, in a fine state of division, shall not 

 take fire. But this precaution does not always suffice to prevent 

 accidents. 



Impressed with these difficulties while experimenting with the 

 red phosphorus, I have sought, by a study of the distinctive 

 qualities of the two kinds of phosphorus to arrive at a safer and 

 more expeditious mode of preparation ; and as the attempts hith- 

 erto made have appealed to methods purely chemical, I have 

 looked more particularly to the physical properties of the two 

 bodies. In this way, I have arrived at a process, which is both 

 simple and rapid, and may be trusted even to inexperienced 

 hands — the last a thing of importance since red phosphorus has 

 become an article of commerce. 



This process depends on the different specific gravities of the 

 two kinds of phosphorus. It consists in putting the mixture 

 into a liquid of intermediate density : thus, the specific gravity of 

 red phosphorus is 2*106, of ordinary phosphorus 1*77; taking 

 now a saline solution of specific gravity between these, — a solu- 

 tion of chlorid of calcium of 38 to 40 B., answers well the pur- 

 pose, — the lighter ordinary phosphorus floats on the surface while 

 the heavier red phosphorus remains below ; and the former is 

 readily taken up by a little sulphuret of carbon which dissolves 

 it, so that the operation can be performed in a closed vessel. 



