366 



Mr. H. M. Vernon on a New 



tube and a thermometer placed in it. In all experiments on 

 the rate of rise of temperature of the phosphorus, the tube 

 was placed in an air-bath kept at 100° by being surrounded 

 with boiling water. The tube of phosphorus was closed and 

 the thermometer kept in position by means of a cork at the 

 mouth ; but no especial precaution was taken to make this 

 tight to prevent air getting to the phosphorus, as a few drops 

 of water forming a layer about 1 millim. thick were always 

 introduced into the tube, and this effectually stopped any 

 oxidation or combustion of the phosphorus, even when it was 

 heated to 100°. In a few cases a thin layer of oil was sub- 

 stituted for the water. The thermometer was graduated in 

 tenths of a degree, and as all readings were taken with a 

 cathetometer, it was read to a hundredth of a degree. The 

 temperature was read at intervals of a quarter or half a minute. 

 The first curve in the figure shows the rate of rise of tem- 



Tcme Ln Minutes 



perature of phosphorus with a well-defined melting-point. 

 The melting-point of this variety was found to be 44°*o, a 

 value found also by v. Schrotter and other observers for octa- 

 hedral phosphorus. The second curve shows the rate of rise 

 of temperature of the other variety of phosphorus. It will be 

 seen that there is no sudden change in the form of the curve 

 at any point, and so it might be thought to be impossible to 



