30 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



In order to reduce the risk of explosion the flask was next 

 heated before sealing. 



" Two ounces of filings of tin, were carefully weighed, and 

 put into a little retort, whose neck was afterwards drawn 

 slender to a very small apex ; then the glass was placed on 

 kindled coals, which drove out fumes at a small orifice of 

 the neck, for a pretty while. Afterwards, the glass, being 

 sealed at the apex, was kept in the fire for above two hours ; 

 and then being taken off, was broken at the same apex : 

 whereupon I heard the external air rush in, because, when 

 the retort was sealed, the air, within it, was highly rarefied. 

 Then the body of the glass being broken, the tin was taken 

 out, consisting of a lump, about which there appeared some 

 grey calx, and . some very small globules, which seemed to 

 have been filings melted into that form. The whole weighed 

 two ounces, and twelve grains " ( Works, II. 393-394). 



"Fire and flame weighed in a balance" by Robert 

 Boyle. Although the observations on calcination which 

 are described under this title l ( Works, 1725, II. 388) agreed 

 closely with those quoted by Jean Rey, Boyle gave a different 

 explanation of the gain in weight, which he attributed to the 

 absorption of heat instead of to the condensation of air. 

 Boyle's failure to recognise the essential part played by air 

 in combustion may be attributed to his observations " Of 

 the strangely difficult Propagation of Actual Flame in Vacuo 

 Boyliano " (New Experiments, touching the Relation betwixt 

 Flame and Air, London, 1672 ; compare Works, 1725, II. 517) 

 in which he found that various substances including sulphur, 

 gunpowder, and fulminating gold, could be fired, although 

 with difficulty, by contact with hot iron in a vessel from which 

 much of the air had been removed by means of an air-pump. 



Boyle's opinion forms the basis of the "Phlogiston" 

 theory of Becher and Stahl. Boyle's view that fire and 

 flame were material things which could be " weighed in a 



1 The title of the original tract is ' ' New Experiments to make the 

 Parts of Fire and Flame stable and ponderable." London, 1673. 



