RESEARCHES ON EVAPOBATION AND DISSOCIATION. 317 



determined by Regnault {Memoires de VAcach'tnio, vol. 21 

 pp. 230, 502 ; vol. 26, p. 520). His results appear to liavo 

 been regarded by himself as possessing no groat claim to 

 accuracy, and quotations are adduced in the original paper, 

 to this effect. If the relation B' = E + c{t'—t) is true, then 

 it is necessary only to determine the vapour-pressures at a 

 few •widely different temperatures, and to compare them 

 with some standard substance. Wo have in this case 

 chosen water. The data are (1), determinations by ourselves 

 at 222-15°, 270-3°, and 280-2°, by an arrangement similar to 

 that described in the paragraph on the dissociation of 

 ammonium chloride (p. 306), but with the space at the closed, 

 end of the U-tube containing only mercury-vapour. The 

 jacketing vapours were mothyl-salicylate and bromonaph- 

 thalone. (2) Regnault's own determinations of the boiling- 

 point of mercury under atmospheric pressure, which are not 

 very concordant ; the mean however cannot be far wrong. 

 (3) Two determinations at the boiling-point of sulphur. In 

 this method, the mercury-vapour, generated in a small bulb, 

 which was heated by the vapour of boiling sulphur, exerted 

 its pressure on a column of mercury confining air, kept at a 

 constant temperature. The pressure was calculated from 

 the alteration of volume of the air. The results aro shown 

 in the following table : 



Batio of ab- 

 aohito temp, 

 of mercury 



and water 'at 

 proBBuro 3>. 



1-G2fi2 

 l-(),504 

 l-()553 

 1-()!)13 

 1-6890 

 l-(i!)40 

 1-0984 

 l-73,'!8 

 1-7359 









Absolute tempera 



Temporatnro 



Temperature 



T't'OHinff* 



tare of water at 



Centigrade. 



Absolute. 



X I VC7£Tl Li 1 V" 



l)re88urc p. 



222-1,5° 



495-15° 



34-4 



304-5° 



270-3 



543-3 



124-35 



329-2 



280-2 



553-2 



157-15 



334-2 



358-46 



631-46 



769-93 



373-36 



357-48 



(i30-48 



768-58 



373-27 



359-27 



632-27 



768-10 



373-25 



358-(i8 



631-68 



760-83 



373-03 



447-0 



720-0 



2896-0 



415-26 



448-0 



7210 



2901-5 



415-36 



