Chemical Constitution of Saline Solutions. 283 
if submitted to the temperature of boiled linseed oil, the red insoluble salt is 
formed. The red insoluble salt may also be made by adding a great excess of 
oil of vitriol to either a green or violet solution of chromic sulphate, and boiling 
till sulphuric acid is evolved ; the red salt is then precipitated. Schrotter ascribes 
the change of colour when violet salts are heated to a loss of water of crystalliza- 
tion, his evidence consisting of the changes referred to above, the salt, Cr,3(SO,), 
being unaffected throughout. Loewel* supposes the violet solutions of chromium 
to contain normal, and the green, basic salts. Kruger} states that when a green 
solution of chrome alum, obtained by boiling the strong solution with water, is 
mixed with alcohol, the spirit takes up a portion of the acid, and the liquid then 
contains K,O-Cr,O;; this green compound is converted into the violet by adding 
sufficient acid to reproduce K,O°Cr,O;°4850;.t Loewel experimented on solu- 
tions of chromium in hydrochloric acid. ‘Two different nitrates of chromium 
exist—one hydrated and crystallizing in octahedra; the other green, uncrystalliz- 
able, and producible by heat. ‘The violet crystals consist of a normal nitrate, 
with nine molecules of water. 
Tichborne attributed the change of colour in chromium solutions when heated 
to a basic condition of the salt, and not to dehydration.§ His method of working 
was to heat a dilute solution of a ferric, aluminic, or chromic salt, either to 100°, 
er, under pressure, to a higher temperature, when the oxides separate out. 
I have heated chromic sulphate, Cr.3SO0,15H,0 to 100° C., when diluted with 
10,000 times its weight of water, without the slightest turbidity resulting, and 
yet a saturated solution of the salt turns green at 70°C., and remains perfectly 
clear. Having weighed all the evidence afforded by our knowledge of chromium 
compounds, I have obtained new facts leading to a definite conclusion as to the 
difference in constitution between violet and green salts of chromium. Loewel 
heated the compound obtained by dissolving chromic hydrate in hydrochloric acid 
to 150° C. The resulting compound, if heated to 300° C., gives partly the violet 
insoluble chromic chloride, Cr,Cl,, and partly the green oxide, Cr,O;, hydro- 
chloric acid being evolved. Therefore, Loewel’s conclusion that the constitution 
of these compounds is that of chromic oxide, combined with hydrochloric acid, is 
not borne out by facts. That the ultimate change leaves chromium in combi- 
nation with chlorine is evidence that these two elements were combined directly 
with each other in the first instance. 
With modern formule, Loewel’s first compound would be Cr,Cl,3H,O, and 
the second might be written thus, Cr,OCl,2H,0; it is an oxychloride, and its 
formation may be thus expressed— 
Cr,Cl,°3 H,O = Cr,0Cl,:2H.0 + 2HCl. 
* Journal fiir praktische Chemie, vol. xxxvii., p. 38. { Pogg. Annalen, vol. 1xi., p. 218. 
{See also Siewert, Ann. der Chemie, vol. 127, p. 86. § Chemical News, 1871, p. 82. 
