r,H. 11 O. = tU. of ben/eno, C,,I I , ..= 1< !. of alcohol. ( '.,1 1 ti < . = -ji in. ot 

 chloroform, ( 1 IK 1 1 ; ,. = (>7, Are. These figures shoxvthe amount of heat 

 expended in converting one part by weight of the above sub-tanee- 

 into vapour. A LjTeat uniformity is olser\ ed if the measure- of heat 



be reftTlvd to the weights of the molecules. For carbon bisulphide 

 the forjiiida ( '>., expre-ses a \\ciuht 7<>, hence the latent heat of eva- 

 poration referred to t he molecular quantitv, C'S.,= 7<> X ( .IO = <S4< >, for 

 et her ='.M ").")('), Tor beii/em^cOOL', f.r alcohol = '.IL'MI ). f , , r chloroform 

 = SUU7. for water HiiM I. v vc. Consequently, for molecular <jiiant it ies. 

 the latent heat varies comparatively lit tie, from 7<nu to lunui) heat 

 units, whilst for single parts by weight it is for water ten time- greater 

 than for chloroform and many others.- 7 



\Ve will cite vet one iiioi'e exa in] ile. showi'iii; tlie direct dependence 

 of tin- properties of a substance on the molecular \\ciuhi. If one 

 molecular part bv weight of the variou> chloride- foi- in-tance. of 

 -odium, calcium, barium. vVc. be dissolved in "Jiii molecular parts bv 

 weight of watt j r ('for instance, in 3(iOO ^rams) then it is found that 

 the greater the molecular weight of the >alt di-sol\ cd. the Create]- is 

 the -pecitic ^rax'itN" of the resultant solution. - s Inu- : 



llo\\c\er. all ]))()] iert ie> of sub-tance- do not depend on the 

 lecular weight alone. 2 ' 1 Xot oidv chemical, but also many physical. 



MI jilipli.-d In lh. lati-iit lii'sit nl' cvajioratii'ii. il.ul :ill i-M-nt-. lirin-'s to li^'lit n 



' . . ill'.---. \\ lliri, , ,| 1|.-|'\\ i-i' I'llK I ' 1 '. ' - ' ' ! ''' I'' '-lilt of iili-cl'. 



M. ...i-ii l,i r i|iian1 it ics \ li.|iii.l- n]>|ir,ir lo c\j>fjnl alnm^l npial amount- <>!' In -a I 



' iilioM 1 . a const a nl quantity. 



i . t lifir Spcrifii ( , i ,, \ it v." I -s7. p. |-j:,. 



1 \m-.u-j ' In- mo ' nti-noil h\ i.j tlir a|i]ilic:itioii . i.l ll n. ct ion ;ii-i -in- i'roin 



- ! . .. o| A: ..-_-, i. in. < .. rlur.lt. an- llio-f -m. -ra 1 1 -a I \< >\, i-otii-i-rninjj ililutr- solutions 

 . l.i-i-n mi-ntioiii-il in tin- Cliap. I. i.Noti I 1 .'. IH. r.n. .M . It i- ln-t iii'cc-sar\ 

 In ' - hiii'l.iiin-ntal .-\|,.-|-inicnt-. 'rraul.r. I't.-if'l'.-r. an.l inoi-.-i'-pi-cially. !>! N'rirs. 

 iilii- -lioui-il lli.it cci-tain |..-riall\ jn-i-pari-d lilni- i ].r.-ci|.ilati'il nu-niliranr < nl 

 .1 - ul.-l i I - nip I.-. lli.,-.< v, hidi an- l'..riin-<l IVoin lln- -.ill- "I coi>i>i-r ;nnl 

 in- |ir.,|,crt y of allos\in^ tin- |M-,I->' of \\ati-r\\liilst 

 i in it. an. I it wa- thiTflor.- i .. il.lc l.\ (hi- in. -an- to 



