Prof. J. Joly on the Apophorometer. 311 



" Pyko-Chemistry. 



" Before passing from the subject of the secondary uses to* 

 which this form of the meldometer may be put, it remains 

 to add that much of the pyro-chemical work done with the 

 blowpipe may with greater ease and delicacy be effected 

 upon the meldometer. Thus, glasses with microcosmic salt 

 or with borax may be made readily upon the ribbon, the 

 colours produced being well seen, and that, too, however 

 deep in tint, where they thin out at the ends along the bright 

 platinum strip. 



"Again, abandoning the use of the ribbon, we may 

 substitute a platinum wire carrying a loop at its centre,, 

 and clamping it in the forceps, form beads of great beauty 

 of the usual form from the action of the hot wire. These 

 may be observed, under the microscope, while hot. Changes 

 of colour, often so characteristic, are very distinctly observed 

 through the microscope [or lens] directed upon the platinum 

 ribbon. For example, the changes of tint of a glass formed of 

 copper oxide (CuO) with borax, coating the ribbon, as the 

 temperature is slowly raised, is from a fine blue through every 

 gradation of tint to a greenish yellow. The command re- 

 possess over the temperature enables these successive changes 

 to be very readily observed. Similarly, the oxidizing effects 

 of the blowpipe may be obtained by addition of oxidizing 

 substances, such as potassium nitrate. Thus, as with the 

 blowpipe, a glass formed of the sesquioxide of cerium and 

 microcosmic salt which is a pale yellow when hot, passing 

 to colourless when cold, may by the addition of KN0 3 

 he intensified to a vivid yellow when hot, to colourless 

 when cold. By the use of reducing agents deoxidation 

 may, of course, be effected. In this way a mixture of 

 cupric oxide with carbonate of soda and cyanide of 

 potassium yields, first the lower cuprous oxide as a trans- 

 parent red crystalline body, and finally the metal which 

 alloys with the platinum. The most minute quantities may 

 be used/" 



Iveagli Geological Laboratory, 

 Jan. 17, 1913. 



