14* ON EVAPORATION. 



ExperimentB I. Spirit of wine. — Evaporated from a furface of four inches 



Jhc'eva^o^rTt^n' *" diameter, 54 grains in 25 minutes: air 53**; aqueous at- 

 of fpirits, ether, mofphere at 49°, and beginningto rain with a moderate breeze. 

 &c. follow the ii would proportionally have been 121 grains from a veflel of 

 fame law as r • u • j- . -tl- • i r 



water. "^ mches in diameter. This gives nearly five grains per mi- 



nute. The fame fpirit boiled at or near 180*. 



Now from the data, water of 83° is equivalent in force to 

 fpirits of 53°; and it may be feen that the evaporating force of 

 water of 83° is nearly 5 in the firft and fecond columns of grain* 

 of the table. It feems probable that the aqueous atmofphere 

 does not diminilh the evaporation of fpirits as it does that of 

 water. 



2. Ether. — 1 . Put a phial containing ether, and a fmall tin 

 veflel of If inch diameter into a fcale and balanced them ex- 

 a6lfy : then poured the ether into the evaporating veflel and put 

 the phial into the fcale again ; took out 40 grains from the op- 

 pofite fcale, and waited till the equilibrium was reftored: this 

 was in 8 minutes 6feconds. The air was 50°, and the ethef 

 at firft 50*^; but it rapidly funk, as was found by dipping a very 

 fmall bulbed thermometer into it, to 28°. In a window with 

 3 moderate breeze. 



. 2 and 3. Repeated the experiment in the fame 

 circumftances, except the evaporating veffel, which was now 

 porcelain, and 2j inches diameter. Loft 40 grains in 3 mi- 

 nutes. Thermometer funk from 50 to 30°. The two expe- 

 riments made this way did not difl^r above one or two grains. 

 Thefe refults reduced to a vefl!el of 3| inches in diameter 

 give 



ift. Experiment, lofs 17 grains per minute; 



2 & 3 — 22f ■ 



The reafon why the refult in the firft experiment was fome- 

 thing lefs than in the other two, was evidently owing to the 

 circumftance of its longer duration, by which the ether was 

 the greater part of the time in a low temperature, and confe- 

 quently evaporated lefs. The ether ufed boiled at 102®. At 

 50° it was therefore in the capacity of water at 160°. But 

 water at 160**, at moft lofesonly 17 or 18 grains per minute, 

 and lefs 20** below that temperature. At firft view therefore 

 it ftiould feem that ether evaporates quicker than the general 

 law afligns. But it muft be allowed that the temperature of 

 the air has fojue effect upon evaporation^ though it has certainly 



very 



