10 Professor Gordon on the Melting Points of Metals. 



1st December, 1841, — T%e President in the Chair. 



The following gentlemen were admitted members: — William Ram- 

 say, Esq., James F. Stewart, Esq., R. D. Thomson, M.D., James Thom- 

 son, Esq., Jan., Thomas Stenhouse, Esq., William More, Esq. 



The following communication was then read: — 



II. — On the Determination of the Melting Points of Metals and 

 various Metallurgic Products, and of the Temperature required for 

 the formation of different Silicates. By Lewis D. B. Gordon, Esq., 

 Regius Professor of Civil Engineering and Mechanics, University of 

 Glasgow. 



In reviewing the state of our knowledge of the melting points of 

 bodies, seven different classes of pyrometers that have been employed 

 or proposed by experimenters were briefly mentioned, and it appeared 

 that the many researches undertaken by philosophers with those 

 instruments afford us only a graduated scale of the fusibility of the 

 substances tried, and do not give the absolute melting points, save for a 

 certain number of metals in their simple state. 



Table No. I. gives the results of different experimenters, from which 

 it appears how little, on the whole, had been done in this important 

 subject until Plattner of Freyberg undertook a most elaborate series 

 of experiments, of which, and of their results, it is the object of this 

 paper to give some account 



Plattner was guided in his course of research by the methods of 

 Prinsep and Daniell, but more especially by the method of de Saus- 

 sure, for determiniijg the melting points. 



Saussure's method consisted in endeavouring to determine the 

 fusing point of a substance in degrees of Wedgewood's pyrometer, 

 according to the diameter of the greatest assay he could fuse before the 

 blowpipe, by comparison with the diameter of the greatest globule of 

 silver he could melt under circumstances in every respect the same, 

 and the melting point of which he knew. 



[The instruments employed, and method of experimenting adopted 

 by Plattner for perfecting this notion of de Saussure, were exhibited 

 and explained.] 



For determining the melting points of the more easily fusible pro- 

 ducts, alloys of gold and silver, and silver and lead, (see Table II,) 

 were employed ; and for those of the more refractory products, alloys 

 of gold and platinum were used. 



The determination of the melting point of platinum was a prelimi- 

 nary step, and this was ascertained by two experiments, as follows : — 



1°. It was found that with a blowpipe supplied with air, under a 

 gentle pressure, from a gasometer, a gold regulus weighing 2290 

 milligrammes, can be fused and maintained in fusion on charcoal, and 



