392 



Dr. W. W. J. Nicol on the 



±000005; and the results show that this was always attained, 

 and in most cases greatly exceeded. 



It was found that a simple interpolation-formula V = 100,000 

 -tt'ct + t^ft, where t'= (t° — 20°), satisfactorily expressed the 

 experimental results. The following Table gives the experi- 

 mental and calculated results for the 18 solutions examined. 

 These comprise the four salts Nad, KC1, NaN0 3 , and KN0 3 , 

 dissolved in water in molecular proportions. The initial tem- 

 perature is 20° C, and seven other determinations were made 

 in each case. The constants for the formulae are given at the 

 foot of each section of the Table. It will be seen that out of 

 125 separate determinations between 45° and 80°, the calcu- 

 lated volume differs from the found in five cases only by more 

 than 9 in the 100,000 ; while the sum of the + and — differ- 

 ences is ( -f 212 — 230) = — 18. There is, therefore, little doubt 

 that the formulae accurately represent the experimental re- 

 sults, and that the latter are correct as a rule to within + 2 in 

 100,000. 



The next point to be examined is the concentration of the 

 solutions. These were, as stated, made of definite molecular 

 composition, but the expulsion of the air caused a change 

 in the strength which is necessarily most marked in the strong 

 solutions. Table III. contains the observed densities at 

 20° C, and the molecular volumes on the supposition that 

 the solutions were of the strength given in the formula. 

 While in the last column of the Table are given the true 

 molecular volumes, where these have been determined. In 

 other cases the volumes calculated from the formulae given in 

 my paper on saturation* are inserted, though these are 

 necessarily only approximate. 



Table II. 



2 NaCl 100 H 2 0. 



4NaC1100H 2 O. 



t 



Found. 



Calculated. 



A. 



t 



Found. 



Calculated. 



A. 



o 



20 



45-4 



504 



56-5 



61-7 



67-6 



72-5 



78-0 



100,000 



954 



1,188 



1,495 



1,758 

 2,079 

 2,364 

 2,699 



100,000 



958 

 1,188 

 1,487 

 1,752 

 2,081 

 2,366 

 2,699 



-4 

 



+8 

 +6 

 -2 

 -2 

 



o 



20 



45-7 



50-9 



56-5 



61-5 



67-6 



72-5 



78-8 



100,000 

 1,059 



1,300 

 1,582 

 1,839 

 2,168 

 2,445 

 2,812 



100,000 

 1,054 

 1,301 

 1,578 

 1,837 

 2,167 

 2,443 

 2,813 



+5 

 -1 

 4-4 

 +2 

 4-1 

 +2 

 -1 



a =30-86; j3= 2703. 



a =357; 0= 0-2061. 



Phil. Mag. January 1886. 



