18 



MACGKEGOR ON THE DENSITY OF AVEAK 



lie A'ery nearly on a straiglit line passing througli the origin. For these solutions, there- 

 fore, the inerease of density, due to (he addition of anhydrous salt to water, is approxi- 

 mately simply proportional to the percentage of salt in the solution thiis formed. 



The agreement of the density of the strongest solution of the above table, with that 

 of the same solution as determined by interpolation in the results of Gerlaoh ' and of 

 Schilf, is shewn by the following numbers : — 



Ac'cording to Scbiff, density = 1^0289 at 20°^5 C. 

 Gerlacb, " = 1^0298 at 15°^ ('. 

 above table, " = 1-0280 at 19°'5 C 



This is the only one of the above solutions with which f>chifi"s and Gerlach's results 

 are comparable. 



Magnesium Sulphate — MgSO,. 



Vohime of bottle to zero mark at 9° -5 C = 2619^6 c.o. 

 !Mas6 of Avater in bottle = 2618 • 9 grm. 

 Mean section of tube = 0^40 sq. cm. 



As in the former table, the first and fourth columns contain the experimental results. 

 The strengths of the solutions examined varied from 0191 to 1'132 per cent, of salt in 

 solution. The fourth and fifth columns shew, that the volumes of all these solutions are 

 greater than those of the water they contain. This salt therefore does not exhibit the 

 same peculiarity as copper sulphate. 



The relation between the concentration and the density of these solutions is shewn 

 graphically in Plate I. The points, whose co-ordinates are the mass of salt per unit 

 mass of solution and the excess of the density over unity respectively, lie very nearly on 

 a straight line passing through the origin. For weak solutions of this salt, therefore, the 

 increase of density is simjily proportional to the percentage of salt in solution. 



So far as I know, there are no existing observations with which any of the above 

 may be compared. Those of Hassenfratz, Schiff, and Gerlach, were all made with solu- 

 tions of greater strength. 



' Gorlacb : Fresenins' Zoitschrift, viii. (1869) 24.' 



