280 Prof. Wohler on Aluminium-leaf. 
chloride of nitrogen; the greater part of the mass is converted 
into violet sesquichloride of chromium, which volatilizes. 
Cr*N+6Cl = Cr?Cl® + NCI. 
Nitride of Sesquichloride Chloride of 
chromium. of chromium. nitrogen. 
By dry hydrochloric acid gas it is with difficulty decomposed at 
a high temperature into sal-ammoniac and sesquichloride of 
chromium, 
Cr?N + 4HCI=NH?# Cl 4 Cr? CI. 
When nitride of chromium, placed in a covered crucible and 
covered with a layer of borax, is heated in a blast furnace, it is 
converted into metallic chromium, a small residue of nitride of 
chromium being left. 
M. Degousse, a goldbeater in Paris, has succeeded* in pre- 
paring aluminium in fine plates like gold or silver. The opera- 
tion of beating is effected in the usual manner, but it is neces- 
sary that the reheating be more frequent ; the fire of a chauffer 
is most suitable. Aluminium-leaf may replace silver in many 
cases ; its white, though less brilliant, is more durable. 
Wohler+ has the following remarks on Degousse’s leaf-alumi- 
nium. It is readily combustible; if heldin the edge of a spirit- 
lamp flame, it takes fire and burns with great brilliancy. It is 
very thin ; a cubic inch only weighs a miligramme. If a leaf of 
it be pressed together, placed in a bulb and heated by means of 
a spirit-lamp in a current of oxygen, it burns instantaneously 
with a dazzling lightning-like appearance. The resultant alu- 
mina is fused, and as hard as corundum. Aluminium wire also 
burns in oxygen like iron; but the combustion does not proceed 
far, for the next parts melt away before they have reached the 
temperature of combustion. Aluminium in the compact form 
does not decompose water, but the leaf, when placed in boiling 
water, decomposes a sufficient quantity to enable the hydrogen 
to be collected. The metal assumes at first a faint bronze sur- 
face colour. After several hours’ boiling, the laminz become 
partially translucent, that is, converted into alumina. If the 
residue be treated with hydrochloric acid, the unoxidized metal 
is dissolved, while the alumina remains undissolved. 
Several of the noble metals, but more especially platinum in 
the finely divided state, have the property of causing a disen- 
gagement of oxygen when placed in sedation of peroxide of 
hydrogen. For this enigmatical phenomenon Schénbein { sug- 
gests an explanation based on the following reactions. 
* Barreswill’s Répertoire de Chimie, October 1859. 
} Liebig’s Annolen, February 1860. 
+ Poggendorff’s Annalen, January 1860, 
