304 
POrULAR SCIENCE REVIEW. 
determiDution of absolute chemical structure may hereafter be achieved, the 
possibility exists very generally, even at the present day, of determining 
relative chemical structure — of making out that in such and such a body 
the structural arrangement is similar to, or dilferent from, that of some 
other and usually more simple body. Hence the importance of studying 
the structural analogies of the simplest organic bodies.” 
The Analysis of Phlormi . — A paper on this subject was recently laid be- 
fore the Royal Academy of Science of Munich by Herren Von Rath and Von 
Gorup. The hicts of the paper relate chiefly to the method of preparing 
this substance from tar containing a large percentage of creosote. The ele- 
mentary analysis of the phloron drawn from creosote of a particular form 
of tar gave results which accord very closely with the 'calculated results : 
0-252 grammes gave 0-G514 of carbonic acid, and 0*1408 of water. 
Calculated 
Found 
96 
70*58 
. 70*49 
8 
5-88 
6*17 
32 
23*54 
. 23*34 
136 
100*00 
100*00 
The Xylol of Coal Tar . — Herr Filteg recently sent a note on this substance 
to the Society of Sciences of Gottingen. The paper is a long one. The 
author opposes all opinions hitherto expressed. He says it is certain that 
paranitrotoluylic, parachlortoluylic, and parabromtoluylic acids, are not pro- 
ducts of substitution of toluylic acid proper. He thinks rather that by re- 
trograde substitution an acid maybe obtained which is isomeric with toluylic 
jicid, and which by strong oxidation will not give terepthalic, but isophtalic 
acid. 
A Beautiful Chrome Green has been produced by M. Casthelaz. The 
method employed is the wet one. The process consists in slowly pre- 
cipitating chrome salts by treating them with hydrated metallic oxides, 
insoluble, or but slightly soluble, in water, or by hydrated metallic 
carbonates, or hydrated metallic sulphides, or again, by salts of weak acids, 
wliich easily leave their bases ; the action is only produced progressively, 
and the oxide of chromium is precipitated in the hydrated form; the colour 
of the compound is magnificent, of a deep emerald green. For this pre- 
paration, it is convenient to adopt economical reagents, such as gelatinous 
alumina, oxide of zinc, carbonate of zinc, sulphide of zinc, &c., whose pi-ice 
is reasonable. The same result may be obtained by treating a chrome salt 
with the non-alkaline metals, which liave a sufficient affinity to unite with 
the acid of the chrome salt and precipitate the oxide. Iron and zinc will 
Ixj more particularly used, as they are cheaper. It is necessary to select 
from among tlie metals, with their oxides and salts, those which, with the 
acid of the chrome salt, give soluble salts as they should be removed by 
washing. If recourse is had to reagents forming, with the acid of the 
chrome salt, insoluble salts, it is only in order to modify the colour and com- 
position of the chrome precipitates and of the green colour thus formed. 
As to the magnificent imperial green colour obtained by M. Casthelaz, it 
}»o88cs8cs properties which will enable manufacturers ultimately to renounce 
the justly condemned and dangerous copper and arsenic greens. The use 
