114 Literary and Philosophical Society. 



attraction of the material to the basis is to be increased by 

 other intermedia. The permanency of the extractive dyes 

 therefore depends on the previous treatment of the cotton, 

 and, where alum is employed, of that salt, so as to procure 

 a more copious precipitation of its earth and to unite it by 

 means of other substances to the material.' 



He observes, however, that Mr. Keir, the ingenious 

 translator of Macquer's ' Dictionary of Chemistry/ appears 

 to have been the first who suspected that the earth of 

 alum was precipitated, and in this form attracted to the 

 material. However, the full explanation seems to be 

 Henry's ; and he also combats the ideas of Macquer on 

 the subject, that chemist having looked to the influence 

 of the alkali which is added, and supposed the alumina 

 to be redissclved, and the alkaline salt with aluminous 

 basis to be the real mordant. The idea of animalising 

 cotton cloth to enable it to take up colouring matter with- 

 out mordant as wool does, also occurred to Mr. Henry, but 

 he acknowledges that Bergman had the same idea ; still 

 it was only an idea, and even now but partially successful 

 as a process of manufacture, although in use and growing. 



Melting of Platinum. 



At a meeting of the Society on Aug 13, 1789, a letter 

 was read from a London chemist, Mr. Thomas Willis, 

 giving an account of the melting of two ounces of platinum 

 in a crucible 3 inches wide on a bed of powdered charcoal. 

 Mr. Henry, junior, is mentioned as being present at some 

 of the experiments mentioned. This must have been 

 William Henry, who would then have been quite a boy, and 

 is soon to be spoken of. 



