g 



Standard Temperature, hi* customary to refer all calculations lor 

 gases to the standard t u- pressure of the atmosphere (760 mm. 



of mercury) ami to the free/ing joini of water. I tag. 



!ii|HTalure f>r uaur and Steam a 



1 is tin initial jK>int for tables of the pro|*-riic* of saturated vapors. 

 But the investor be nu- h (imalent of hrat by Rowland 



resulted in a determination of ' rat of water with much greater 



MM is possi! mil's method of mixtures, and showed 



that tin- in-i .'-m: Mot well adapted for thr standard lcm|jeraturc 



It has In-en thr habit of many ph\>it Uu for many years to 

 i5C. as the standard temjierature, and this corresponds substan- 

 tially with 62 F., at which the Knglish units of measure are standard. 

 Mechanical Equivalent of Heat. - most authority nnina 



f the nu-i hanii al r<jui\aK-nt of heat appears to be that by Rowland,* 

 from which tin \\ork n .juir<l to raise the tem|K-rature of one pound of 

 water from 62 to 63 F. 



778 foot-|M>unds. 

 i> equivalent to 



427 UK ;r< kilograms 



in the m< ii> important 



ant has been ii. tl \jH-rinn-nti -r>, and 



also a rccomputation of his results has l>een mad* rccompartsoii 



of iii- thermonn u r-. 1 ! ion appears to be that his results may 



be a little small, but the differences arc not important, and it is not certain 



(inclusion is valid. There >eem>. tin i <> sufficient reason 



uinginK the accepted \al t above. 



Specific Heat of Water. The most reliable determination of the 



is that by Dr. Barnes, t who used an clet 



methcxl devised i (\dlendarand him-elf, and who extended 



the method to and In-low ti ..jnt l>> carefully c(x>lin>; water without 



rmation of i to 5 C. This methcxl lative results with 



great refinement, and gives also a good confirmation of Rowland's d 



niination of the mechanical equivalent of heat. Dr. Barnes reports 



values of the specific heat of water up to 95 C. In the following table 



l are quoted from o to 55 C.; from 55 to 95 his results have 



v. Am. Ac*l. t voL x vU), 



t Pkysieal flrwru-.voL xv, p. 71, 1901 



