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POPULAR SCIENCE REVIEW. 
the instant that the compressed and cooled gas exchanged the intense pressure 
for that of the atmosphere. 
Plant Chemistry . — Professor Church has examined colein, the red 
colouring matter of Coleus VerschaJJeltii, and is inclined to think that it is 
identical with oenolin, obtained from red wine, as well as with the substances 
anthocyan, erythrophyll and cyanin, which have been extracted from blue 
and purple flowers. Colein is soluble in alcohol, but insoluble in ether ; 
acids turn its solutions red, while alkalies strike a violet, indigo-blue, green, 
and, finally, yellow colour. The formula of colein is C 10 H 10 0 5 ; the 
salts which it forms with lead, barium, and other metals, have been prepared. 
It appears to be present in the copper-beech and the grape, and it is 
perfectly distinct in its characters from the colouring-matter of the red beet. 
The composition of the flowers of Fraxinus excelsior has also been investi- 
gated by Professor Church. He found the ash to contain 39*42 per cent, 
of potash, 13*22 per cent, of lime, and 28*98 per cent, of phosphoric acid. 
The ash-flowers contain 7*4 times as much nitrogen, 7*7 times as much 
potash, and 10*5 times as much phosphoric acid as has been found in the 
leaf-scales of the beech. His paper (“ Journal of Botany,” 1877, vi. 346) 
contains, moreover, some interesting observations on the composition of the 
leaves of a variegated form of Acer Negundo. The ash of the white and 
green portions were analysed separately with the following results : — 
Percentage in Ash of White Parts. Green Parts. 
Potash 40*05 12*61 
Lime ...... 1089 39*93 
Magnesia 3*96 4*75 
Phosphoric Acid .... 14*55 8*80 
These figures seem to show that the white leaves, or parts of leaves, of 
this maple differ from the green leaves much in the same way that young 
leaves differ from old. 
The Behaviour of Sulphates with Melted Sulphur. — Sestini has shown that 
gypsum when heated with sulphur decomposes in accordance with the 
equation : — 
CaS0 4 + 2S = 2S0 2 + CaS. 
Violi has since observed that this reaction appears to be a general 
reaction as regards the sulphates. Sulphates of the metals of the alkaline 
earths, as well as those of aluminium, chromium, zinc, manganese, iron, 
cadmium, lead, bismuth, copper, antimony, and mercury, are converted into 
sulphides in accordance with the equation, RS0 4 + 2S = RS + 2S0 2 . 
The author recommends this method for the formation of a metallic 
sulphide, and also as a source of sulphurous acid ( Ber . Deut. Chem. 
GeseU., x. 293). 
Preparation of Nitrogen. — It has been observed by Gatehouse (“ Chemi- 
cal News,” xxxv. 118) that ammonium nitrate and manganese peroxide, when 
heated together at a temperature of 165°-200° C., evolve a constant current 
of an invisible gas, which neither burns nor is absorbed by potash pyrogal- 
late. The gas proves to be pure nitrogen, formed in accordance with the 
equation : — 
4 NH 4 NO a + Mn0 2 = Mn (NO,) 2 + 8 H 2 0 + 6N. 
