4 JOURNAL OF THE 
apparently no influence. As to the action of alkalies, 
sodium or potassium, or ammonium hydroxide, or the car- 
bonates, readily turned the violet solutions green. They 
had no action upon green solntions. 
CHANGES IN PHYSICAL PROPERTIES. 
In the case of chromic sulphate, Sprung’ has shown 
that the violet solution with about twenty-four per cent. 
of the salt has the specific gravity 1.1619. while the 
green is 1.1486. So too with the alum there is an in- 
crease of volume, which has been noticed by Siewert and 
also by Mohr,’ and a decrease of volume is observed as 
the green solution reverts to the violet. Lecoq de Bois- 
baudran* has also observed these changes, noting that 
they are independent of the concentration of the solution, 
the presence of crystals, or whether the vessel is open or 
closed. The changes in density can be reckoned from 
his dilatometric observations. Dougal’ has shown that 
the alteration in density of even a dilute solution of 
chrome-alum, after boiling, may readily be detected by 
a specific gravity bottle. In this manner, one, two and 
a half, and five per cent. solutions were experimented 
upon. ‘The actual amount of change depended upon the 
duration of the heating and the length of time which had 
elapsed since the green solution had been prepared. The 
violet solutions became specifically lighter when changed 
to green by boiling. The transformation is accompanied 
therefore by expansion. 
According to Sprung the violet and green solutions 
show a difference in internal friction or viscosity. The 
ratios af diffusion out of capillaries at temperatures 10° 
20°, 30°, 40°, 50°, of the green to the violet were as 100 
iN. Arch, ph. nat., 53, 112. 
2 Ber. d. chem. Ges., 4, 318. 
8 Compt. rend., 79, 1491, 
4J. Chem. Soc. Lond., 7896, 69, 1597, 
