AQUEOUS SOLUTICNS—MACGREGOR., 261 
Art. I.—On tHe RevativE BuLK oF CERTAIN AQUEOUS 
SOLUTIONS AND THEIR CONSTITUENT WATER.— 
By Pror. J. G. MacGregor, D.Sc. 
(Read Jannary 11, 1886 ) 
THE fellowing experiments were made with the ‘object of 
‘determinizg whether or not weak solutions of Sodium Phos- 
phate and Carbonate have volumes which are less than the 
volumes at the same temperature of the water which they con- 
tain. 
Professor Ewing’ and J had found that sufficiently weak soiu- 
tions of sulphate of copper contain amounts of water whose 
volumes if free would be greater than those of the solutions 
themselves; and that anhydrous copper sulphate, added in small 
‘quantities to water, produces solutions of smaller bulk than the 
original water. It seemed desirable therefore to extend the 
investigation to other hydrated salts. 
The apparatus employed consisted of dilatometers, which were 
large glass bottles (commonly called Winchester quarts), with 
glass tubes fitted in their necks. The bottles had capacities of 
about 2,600 cc. The glass tubes were about 25 em. in length 
and 0-4 sq. em. in section, and were chosen so as to be as uniform 
in bore as possible. They were fitted to the bottles by means of 
India-rubber stoppers, and fitted so tightly that there could be 
no danger of any relative displacement of tube and bottle. The 
rubber stoppers were held fast to the bottle by wires. Their 
inner ends were hollowed conically, and the glass tubes started 
from the summits of the conical hollows, so that air bubbles 
could easily be made to pass up the tubes. At their upper ends 
the tubes widened into funnels. Fine scratches on the tubes 
served as zero marks. ‘The bottles stood in a large zine bath up 
to their necks in water. The dilatometers were calibrated by 

1'Trans. Roy. Soc. Edin., vol. xxvii. (1873) p. 51; Reports Brit. Asso. (1877) ; 
‘Trans. Roy, Soc. Canada, vol, ii, (1884) sec. iii., p. 69. 
