270 



Force of vapor 

 of liquid am- 

 monia} 



of muriate of 

 lime. 



Forces of the 

 vapour of mer- 

 cury and ful- 

 phuric acid. 



ON THE FORCE OF STEAM OR VAPOUfe 



TIlis rather exceeds the force of aqueous vapour at an eqtial 

 diftance from (he boiling point ; but it is no more than may be 

 attributed to unavoidable little errors in fuch experiments. In 

 a barometer tube the fpirituous vapour at 60°, over the mer- 

 cury, deprefles the column about 1.4 or 1.5 inchesj which 

 is fomething lefs than the due proportion ; one caufe of this 

 may be the evaporability of fpirits, which in operating onf 

 fmall quantities, quickly diffipates part of their ftrength* 



Experiments on Liquid Ammonia. 

 Liquid ammonia or volatile alkali^ the fpecific gravity of 

 which was .9474, boiled near 140°; in the barometer a 

 fmall quantity deprefTed the mercury 4.3 inches in the tem- 

 perature of 60°. In higher temperatures it did not produce 

 a proportional depreffion; becaufe the moft volatile part of 

 the compound, expanding in the vacuum of the barometer, 

 leaves the reft more watery, and confequently its vapour muft 

 be weaker ; efpecialiy when the portion ufed is connned to a 

 drop or two. 



Muriate of Lime, 

 Put a portion of liquid muriate of lime over the column of 

 mercury in a barometer. The boiling point of the muriate 

 was found hy experiment to be 230°. At 55° the depreffion 

 was ,22 of an inch : 



at 65°— .30 



— 70°— .40 ^ 



^ 95°— .90 

 all which nearly agree with the forces of aqueous vapour IS<* 

 below the refpedive temperatures. 



Mercury and Sulphuric Acid. 

 Mercury boils by my thermometer at 660°, and fulphurlc 

 acid of the fpecific gravity 1,83, boils at 590". It is very 

 difficult to determine the precife force of vapour from thefe 

 liquids in any temperature under 212° ; becaufe at fuch great 

 di (lance from the boiling point the vapour is fo weak as to be 

 in efTec! almoft imperceptible. Following the general law, 

 the vapours of thefe fluids ought to be of the force .1, mer- 

 cury at 460°.. and fulphuric acid at 390°.— Col. Roi makes 

 the expanfion of 30 inches mercury by ISOq of heat = 

 .59e9 or .5u51 ; and in a barometer the expanfion in the 



feme 



