284 Hartiny—TVhe Action of Heat on the Absorption Spectra and 
The first action of a temperature of 300°C. is then represented as follows :— 
2CrOClHEO = CrCl, or Cr, OF + 2HCl + 181,(0), 
Schrotter’s and Loewel’s experiments lead to similar results, but are applied 
to different compounds. 
When Kruger operated on a strong solution of chrome alum, he found that 
from the violet solution the original salt was precipitated by alcohol. If the 
solution was boiled until green, and alcohol then added, the green salt was 
precipitated as an oily liquid, and the alcohol contained a portion of the 
sulphuric acid. The change of colour, therefore, he said, was due to the produc- 
tion of a basic compound. On repeating this experiment, and extending it to 
other salts, such as the chromic sulphate and chromic nitrate, similar results 
were not obtained. I operated in the following way, taking four grams of each 
salt and dissolving it in 40 c.c. of water. The liquid was divided into two equal 
parts; one was precipitated by alcohol, the other was boiled, allowed to cool, and 
alcohol in gradually increased quantity added, but the result was only a green 
solution. The violet hydrated salts, therefore, are insoluble in alcohol, while the 
green compounds are soluble. It occurred to me that Kruger had added alcohol 
to the hot liquid, and so obtained a decomposition of the salt; I therefore took a 
boiled solution, cooled one-half, which still remaimed green, and made both 
liquids up to the same bulk with alcohol. The hot solution rendered a green oil- 
like precipitate ; the cold one, however, did not do so. We cannot, therefore, 
consider it proved that a basic salt existed in both these solutions. 
When the so-called chromic hydrate, Cr,O;°9H,0, is dissolved in nitric acid 
and kept quite cold, it forms at first a purple solution, but after a certain amount 
of the acid has been saturated, the solution turns green, the return to a purple 
colour being caused by a further addition of acid. The green solution is 
uncrystallizable; the purple, as I have already mentioned, does crystallize. 
Schrotter* found that, if as much chromic hydrate as possible is dissolved in 
sulphuric acid, a green liquid results which contains the salt, Cr.0;°250; (A) :— 
Oren ; > Mpild 50°68 per cent. 
Gs . «o o @6i AML 
100:00 99:99 
When a solution of this salt is boiled, a green precipitate separates which has 
the composition 3Cr,0;'°25O; (B), with probably six molecules of water. 
If the green solution obtained by boiling the violet salt be contained in the com- 
pound (A), it ought, on the addition of a large quantity of water and subsequent 
ebullition, to precipitate the compound (B). But it has already been stated that 
* Poge. Annalen, vol. lii., p. 513. 
