Prof. Graham on the Diffusion of Liquids, 187 



1*0213, 1*0285. The increase of density corresponds very 

 nearly with the proportion of chloride of sodium in solution. 

 A close approach to this direct relation is indeed observable 

 in most salts, when dissolved in proportions not exceeding 4 

 or 5 per cent. • 



The relation which appears in these results is also favour- 

 able to the accuracy of the method of experimenting pursued. 

 The variation from the speculative result does not in any ob- 

 servation exceed 1 per cent. 



(2.) Is the quantity of salt diffused affected by temperature? 



The diffusion of similar solutions of chloride of sodium was 

 repeated at two new temperatures, 39° # 6 and 67°, the one 

 being above and the other below the preceding temperature. 

 It was necessary to use artificial means to obtain the low tem- 

 perature owing to the period o'i the season. A close box of 

 double walls, namely the ice-safe of the Wenham Ice Com- 

 pany, was employed, masses of ice being laid on the floor of 

 the box, and the water-jars supported on a shelf above. The 

 water and solution were first cooled separately for twenty- 

 four hours in the ice-box, before the diffusion was commenced. 

 It was found that the temperature could be maintained within 

 a range of 2° or 3° for eight days. It was doubtful however 

 whether the temperature was constantly the same to a degree 

 or two in all the jars; and the results obtained at an artificial 

 temperature were always less concordant and sensibly inferior 

 in precision to observations made at the atmospheric tempe- 

 rature. 



Diffusion of Chloride of Sodium. 



Proportion 



of salt to 100 water. 



Diffusion product. 



In grains. 



Ratio. 



1 

 2 

 3 

 4 



1 

 2 



3 

 4 



At 39°-6 

 At 39°-6 

 At 39°-6 

 At 39°-6 



At 67° 

 At 67° 

 At 67° 



At 67° 



2-63 



5-27 



7-69 



1000 



350 



6-89 



9-90 



13-60 



1- 



200 



2-92 

 3-80 



1- 



1-97 



2-83 

 3-89 



The proportionality in the diffusion is still well-preserved 

 at the different temperatures. The deviations are indeed little, 

 if at all, greater than might be occasioned by errors of obser- 

 vation. The ratio of diffusion, for instance, from the solutions 

 containing 4 parts of salt, is 3*80 and 3*89 for the two tem- 

 peratures, which numbers fall little short of 4. 



The diffusion manifestly increases with the temperature, 



