TRANSACTIONS OF SECTION B. 469 
If the naphthalin is digested with the chloride of aluminium at a lower tempera- 
ture, obtained either by mixing it with benzol or heating it in an oil-bath to 160°, 
the products are altogether different. 
In this case the products have a much higher boiling point, consisting chiefly 
of isodinaphthyl which may be separated from the oils that accompany it by crys- 
tallisation from benzol or petroleum ether. 
This isodinapththyl melts at 187°, and boils at 485° (by air thermometer), and 
yields a picrate greatly resembling that of naphthalin. The liquid portion, distilled 
again with aluminic chloride, gave benzol, naphthalin, and hydrides of naphthalin, 
while the isodinaphthyl treated in the same way was almost completely carbonised. 
We may therefore conclude that naphthalin gives isodinaphthyl and hydrides 
boiling at a high temperature, and that these latter afterwards produce benzol and 
naphthalin hydrides. 
Benzol is not affected atits boiling point, but if heated with aluminic chloride 
in sealed tubes to 235° C. it becomes very brown, and on opening the tube a good 
deal of gas escapes ; this gas burns with a pale flame, and the contents of the tube 
distilled with water give hydrocarbons boiling from 80° to 160°. When the tem- 
perature does not rise above 200° no gas is found in the tubes, even when these are 
heated for eighteen hours. On fractionation two-thirds of benzol is recovered, the 
rest consists of toluol (whence benzyl chloride was prepared in order to establish 
its identity), ethylbenzol, and a portion boiling above 200° which on crystallisation 
from alcohol melts at 69° and boils at 250-255°, and has the properties of diphenyl. 
Diphenylmethane distilled with aluminic chloride gives a mixture boiling at 
80°-120°, containing benzol and toluol. 
Triphenylmethane distilled with more than half its weight of chloride of 
aluminium gave only benzol. Triphenylmethane, mixed with seven times its weight 
of benzol, and heated with chloride of aluminium for two days in an oil-bath to a 
temperature just below the boiling point of the mixture, gave nearly half its weight 
of diphenylmethane. 
Hexamethylbenzol heated with one-third of its weight of chloride of aluminium 
for three-quarters of an hour gave off plenty of a non-illuminating gas, and left a 
product boiling at 200-220°, from which crystals of durol were deposited (melting 
at 97°), the mother liquor being the isomeric tetramethylbenzol. 
Durol gives off gas, a portion boiling at 150°-160°, the chief portion at 190°— 
200° containing trimethylbenzol mixed with some xylol. 
In the case of the poly-substituted methyl benzols one or more methyl groups 
is displaced by hydrogen; in all cases very little hydrochloric acid is given off. 
In order that the same hypothesis may explain both the destructive and the 
synthetic action of aluminic chloride, the authors suggest that whereas they have 
formerly assumed that the equation C,H,+A1,Cl,=C,H,Al,Cl,+HCl repre- 
sents the first stage in the synthetical reactions, so this same equation is also the 
first stage of the present decompositions. They assume that the compound of 
©,H,A1,Cl, is broken up by heat into diphenyl and subchloride of aluminium, and 
that the latter is decomposed by the free hydrochloric acid into aluminic chloride 
and hydrogen, and that it is the hydrogen thus set free that exerts the reducing 
action observed. 
Thus benzol is reduced to the groups methyl and ethyl, which give rise to 
methyl] and ethylbenzol. 
: Naphthalin forms dinaphthyl and its hydrides, the latter giving naphthalin 
ydrides. 
In the case of di- and tri-phenylmethane and the methylated benzols, the group 
AJ,Cl, seems to displace a phenyl or methyl group, which, under the reducing 
action of the mixture, appears as benzol or methane respectively. 
It is also to be observed that a quantity of carbonaceous matter, evidently 
poor in hydrogen, is always formed. 
4. On the Nitrates in Soil. By R. Wartnetoy, F.C.S. 
