TO Speyers — Heat of a Change in Connection noith 



The water equivalent of the calorimeter and fittings con- 

 tained an uncertainty of less than 0*2 per cent. In calculating 

 the water equivalent of the solution, 0*5 was taken as the 

 specific heat of the solute and that value given in L. and B.'s 

 Tabellen as the specific heat of the solvent, and the sum of 

 these as the specific heat of the solution. The quantity of 

 solution was small in comparison with the 500^^^ of water and 

 so this introduces an uncertainty of likewise less the 0*2 per 

 cent, of the total water equivalent. 



Let q be the total water equivalent, then the heat of solution 

 is (TdzO'OOl) (^dbO'OOl^). Let n be the number of grammole- 

 cules of solute in 100 grammolecules of saturated solution, ni 

 the molecular weight of the solute and M that of the solvent, 

 w be the weight of solvent run into g and d the weight of 1*^^ 

 of solute, that is, its density. Then letting Q refer to V"" of 

 solute we have 



(T±0-001) te±0-001g) '°°-("^^'') M^^=Q±AQ. 



The expressions Ln and AQ represent the uncertainties in the 

 respective quantities ; A?i, the uncertainty in reading n from 

 curve ; AQ, the uncertainty due to the uncertainties on the 

 left. These uncertainties on the left were combined to make 

 a maximum effect and a minimum effect and the mean of these 

 two values was taken as Q, the variation of this mean value 

 from either of the extreme values giving AQ. 



The quantities M, m, w and d were taken without any uncer- 

 tainty ; the molecular weight, because M and m contain about 

 the same elements, and being in the form of a quotient the 

 uncertainties have a small effect upon Q ; w and c?, because 

 their uncertainties lie in the third decimal place. The atomic 

 weights used are C =12, H =1, O =16, JST =14, CI =354. The 

 uncertainty in reading from the solubility curve was never 

 more than 0'4 grammolecules and usually not more than 0'2 

 grammolecules; that is (A/z. was never >0"2 and usually 

 A?i = 0-1). 



The heats of solution are given in the large table following. 



The densities of solvents and solutions were taken from 

 j)lots of 23ublislied data and will be found in the large table 

 with their uncertainties. 



In applying equation 5 to the present system, we must 

 remember that the initial state involves two bodies, solvent 

 and solute, while the final state involves only one, the solution. 

 Putting the volume of the solute for convenience equal to 1% 

 we have from tt or from 5 



