3*4 



METHOD OF DISTILLING 



The contrivance too, of having the under part of the 

 alembick, where the condenfed vapour is collected, or 

 upper part of what they call the adkur, of earthen-ware, 

 of fo great a thicknefs, and of courfe at fo great a 

 diftance from the heat in the body of the ftill, is well 

 imagined to keep the fpirits the coolefl poflible, when 

 collected, and running off. 



By thus cooling and condenfrng the vapour, likewife, 

 fo fuddenly as it rifes, there is in a great meafure a con- 

 ftant vacuum made, or as much as poflibly can be ; 

 but, that both fleam arifes falter, and that water boils 

 with much lefs'heat, when the prefTure is taken away 

 from its furface, is an axiom in chemiftry too well 

 known to need any illuftration; it boiling in vacuum, 

 when the heatis only ninety or ninety-five by Farenheit's 

 thermometer ; whereas in the open air, under the pref- 

 fure of the atmofphere, it requires no lefs than that of 

 two hundred and twelve ere it can be brought to the 

 boiling point. . 



I muff further obferve, that the fuperior excellence 

 of condenfrng the vapour fo effectually and fpeedily in 

 the alembick, to our method of doing it in a worm and 

 cooler, is greatly on the fide of the former; both from 

 the reafons I have already adduced, and becaufe of the 

 fmall ftream of vapour that can be only forced into the 

 worm, where it is condenfed gradually as it defcends ; 

 but, above all, from the nature of vapour itfelf, with 

 refpeft to the heat contained in it, which of late has 

 been proved, by the very ingenious Dr. Black, to be 

 greater by far than, before his difcoveries, was ima- 

 gined. For vapour he has (hewn to be in the ff ate of 

 a new fluid, where water is difTolved by heat j with the 

 alhftance, perhaps, if I may be allowed a conjecture, 

 of the air which it contains: and all fluids, as he has 

 clearly demonftrated, on their becomin abforb 



3 vrtaiji 



