0!^ EVAPORATION. J^f 



P:x(imple. Let the point of condenfation be 52^, the tera-Ufe of the table 

 perature of the air 65^, with a moderate breeze. fuftrited! *'" 



The number oppofite ,52° in the fecond column of grains is 

 2.06, and that oppofite 61)*^h 3A6; the difference, 1.1 

 grain, is thfe evaporation per minute. 



PROBLEM ir. 



Having given the quantity evaporated in a minute, found by 

 experiment, and the temperature of the air, to find the force 

 of the aqueous atmofphere, and the point of condenfation^ 



Solution. Subtra6l the obferyed evaporation from that op- 

 pofite the given temperature in the table; and look above for 

 the number neareft to the remainder in the fame column of 

 evaporation, oppolite to which will be found the force of the 

 aqueous atmofphere, and the point at which it begins to be 

 eondenfed. 



Example. Finding the evaporation from a veffel of fix 

 inches in diameter to be 1. 7 grain per minute with a brilk 

 wind, air 62° ; what is the weight of the aqueous atmofphere, 

 and the temperature at which it begins to be eondenfed into 

 water.'' 



The number oppofiie 62° in the third column of grains is 

 S..52, being the whole evaporating force at that temperature 

 in a perfediy dry atmofphere; from which take. 1.7 grains^ ' 



the real evaporating force obfeived, and the remainidery 

 1.82, correfponds, as per table, to the force .294" inches of 

 mercury, the weight of vapour, and to 43° of temperature.* 



Evaporutlon of Spirits, Etha\ S,'C. 

 If the law of evaporation above given apply to water in ExperlTnents 

 every part of the fcale of heat, no reafonable doubt can be ^^'^^^ ^^^w tfiat 



-^ '. , ' ^ , the evaporation 



entertained refpefting its application to other liquids. I have of fphits, ether, 

 notwitlifiandin^ made feveral experiments on others, the re- ?^* ^p^'^^^^* 

 fults of which are conformable to the fame law. Some of them water, 

 follow : — 



* It may be proper to remind the reader that all the experiments 

 on evaporation are underftood to be made in the open air, or in a 

 window with a current inward ; alfo it may be obferved the evapo- 

 ration in a ciofe room is much lefs and is beCdes irregular, being 

 greater proportionably from a lefs furface, evidently from the ftag-. 

 nation of the air. 



] . Spirit 



