310 Prof. J. Joly on the Apophorometer. 



u As regards compounds, the command we have over the 

 temperature in the meldometer enables many very distinct 

 separations to be effected. Thus, dealing with realgar, at 

 low temperatures, the substance is sublimed in a rich yellow 

 sublimate. Somewhat higher a decomposition is effected, 

 the free arsenic showing as a white sublimate of the oxide 

 round an eye of sublimed realgar. As the temperature rises 

 the effect is more and more that proper to arsenic only, the 

 liberated sulphur not appearing ; but the eyes remain most 

 generally distinctly touched with realgar. Orpiment behaves 

 in a similar manner. Pyrargyrite, a compound of silver and 

 antimony sulphides, throws off the antimony first in a rich 

 white sublimate of the oxide, touched more or less with a 

 pale pink cloud, probably the unaltered compound. A bead 

 of silver is left upon the ribbon, which ultimately volatilizes 

 to the grey-black sublimate of silver. Clausthalite, the 

 selenide of lead, affords first a sublimate of selenium, a fine 

 ash-red ; this then becomes veiled over and intermixed with 

 the rich yellow and whites of the lead oxides, so that a 

 A^ery beautiful marbling is produced, which shows stronger 

 tints of red seen from the back of the glass than from the 

 front. 



" Many such effects are seen in a similar order with the 

 blowpipe, but are not produced with the ease, certainty, and 

 cleanliness obtaining with the meldometer. Tests may very 

 conveniently be applied to these sublimates as they repose 

 upon the glass, in the knowledge that the only addition to 

 the original substance can be oxygen. Sublimates also may 

 be obtained from very minute quantities of the substance. 

 This is an advantage in more ways than one 



" But the meldometer is cnpable of affording sublimates 

 which the blowpipe very certainly will not reveal. Thus, 

 for example, tourmaline affords a pale whitish-yellow sub- 

 limate, the nature of which I have not determined ; and 

 enstatite volatilizes at the highest temperatures obtainable,, 

 very nearly, giving a pale brown sublimate. An addition 

 may be made to this form of the meldometer, which will 

 permit of sublimates being obtained in the absence of free- 

 oxygen." 



[Here follows the description of a closed sublimation vessel 

 with tubulures by which an indifferent gas may be admitted 

 and which has glasses supported both above and below 

 the ribbon for catching the sublimate.] " In this manner 

 sublimates of realgar and arsenic may be made to afford the 

 unoxidized substances." 



