HIGH PRESSURE BRIDGMAN. 



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raised to from 12,000 to 13,000 kilograms. The transition from 

 white to black phosphorus occurs under these conditions in from 5 to 

 30 minutes. The pressure drops at first very slowly, then more 

 rapidly, until apparently a critical point is reached somewhere be- 

 tween 11,000 and 12,000, at which it drops suddenly to about 1,000 

 kilograms. Pressure may then be increased again (with the form 

 of apparatus used this secondary increase could not be carried 

 beyond 11,000 kilograms) with no further drop of pressure. On 

 cooling the lower cylinder and relieving pressure, the white phos- 

 phor is found transformed into a black substance of very much 

 smaller volume than the original white phosphorus. Proof will be 

 given presently that this is a modification of phosphorus, not a com- 

 pound. This experiment has been repeated successfully every time 

 that it has been tried, now five times in all. About 50 grams of 

 black phosphorus may be formed at a time. 



An attempt to form black phosphorus from white at 175° and 

 nearly 13,000 kilograms was without success. Also an attempt to 

 produce black phosphorus from commercial powdered red phos- 

 phorus, which had been inoculated with a small piece of black phos- 

 phorus, was without result in 40 minutes at 12,900 kilograms and 

 200°. Another attempt to produce black phosphorus from the mas- 

 sive red phosphorus, to be described later, was also unsuccessful after 

 30 minutes at 12,900 kilograms and 200°. 



The black phosphorus presents two distinct characteristic frac- 

 tures. In some places the fracture is coarsely granular like sugar, 

 apparently crystalline, but the grains under a low-power microscope 

 show no semblance of crystalline form. In other places where the 

 flow under pressure was great, the fracture is fibrous with a metallic 

 luster, very much like graphite in appearance. In spite of the high 

 pressure of formation, the mass of the black prosphorus is permeated 

 with pores, some of which may be several millimeters in diameter. 

 These pores may at first be filled with kerosene. The presence of 

 these pores doubtless accounts for the slight apparent increase in 

 w T eight of the specimen after the transformation. 



In order to prove that the substance formed was really a new modi- 

 fication of phosphorus and not a compound, a colleague very kindly 

 made an analysis of two samples at the chemical laboratory of Har- 

 vard University. The results of the analysis are as follows: 



136650°— 20- 



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