Jury 8, 1915] 
NATURE 
599 

The nitro-glycerine high explosives used in 
mining are unsuitable for shell filling, owing to 
the sensitiveness of nitro-glycerine to shock, 
which would cause premature detonation in the 
bore of the gun. The ammonium nitrate group 
of high explosives, also used in mining, which 
contain nitro-hydrocarbons, and in some instances 
aluminium, have been advantageously adapted for 
shells. Although the hygroscopic nature of 
ammonium nitrate is detrimental, this may be 
successfully overcome. 
Abel, in 1865, first proposed the use in mines of 
compressed wet gun-cotton fired by means of a dry 
gun-cotton primer; this was later used for filling 
torpedoes, but it has the disadvantage of low 
charge density. Gun-cotton cannot be compressed 
to a greater density than 1°25. In other words, 
a torpedo head which would hold 125 lb. of com- 
pressed gun-cotton could hold from 160 to 180 |b. 
of the denser trinitrotoluene or picric acid, with 
a corresponding increase of destructive power. 
Sprengel, in 1875, first showed that picric acid 
could be detonated, and in 1881, Turpin, in 
France, demonstrated the practical possibility of 
using it for filling shells. The idea was rapidly 
taken up by other countries. 
The methods of manufacturing nitro-hydro- 
carbons suitable for shell filling are very similar 
to those in use for producing nitro-glycerine. A 
mixture of sulphuric acid and nitric acid is used, 
and large quantities, very frequently as much as 
a ton or even more, are made in one operation. 
To obtain the highest yields of pure products very 
great attention must be paid to the composition 
of the acids, to the efficiency of agitation, and 
to the temperature, which is regulated by internal 
heating or cooling coils. 
Picric acid, discovered in 1771 by Woulfe, of 
London, when used for filling shells has a 
different mame in each country. It is called 
Mélinite in France, Lyddite in England, Pertite 
in Italy, Shimose powder in Japan, Granatfillung 
88 in Germany, and Ecrasite in Austria. It is 
not always employed in the pure state, there being 
occasional addition of crésylite (trinitrocresol) or 
a salt of that substance, the object of which is 
to reduce the temperature of fusion. It is manu- 
factured from phenol (carbolic acid, obtained from 
the distillation of coal-tar) by first dissolving in 
sulphuric acid and then treating the resulting 
phenol-sulphonic acid with nitric acid in excess. 
It forms yellow crystals with an intensely bitter 
taste. It has a specific gravity of 1°777 and melts 
at 122°5°C. Picric acid, if heated gradually, 
takes fire without explosion, giving rise to dense 
black smoke, but the application of a red-hot rod 
will cause it to detonate, as will also the ex- 
plosion of a capsule of fulminate of mercury. 
Owing to the readiness with which it forms certain 
unstable metallic salts, the use of picric acid is not 
free from danger, and it is largely on this account 
that it is being rapidly replaced by the somewhat 
less energetic but much safer trinitrotoluene. 
Trinol, trotyl, trilite, tritolo, or T.N.T., as tri- 
nitrotoluene is variously called, is made from 
NO. 2384, VOL. 95] 

toluene (obtained from coal-tar naphtha), and was 
first proposed for use in shells by Haiissermann, 
in 1891. The result of the first nitration of toluene 
is a mixture of mono-nitro-toluenes, which are then 
treated with a mixture of strong nitric acid and 
sulphuric acid, and raised to the third or trinitro 
degree of nitration in one stage. Trinitrotoluene, 
when pure, forms brownish-yellow crystals with a 
melting point of 81° C. It is very stable, not 
igniting below 300°, but when it explodes it does 
so with great violence. Its density when melted 
varies between 1°57 and 1°60. Neither picric acid 
nor trinitrotoluene can be detonated with cer- 
tainty by fulminate of mercury, and a small quan- 
tity of an intermediate priming charge is 
employed. In the case of trinitrotoluene, the use 
of tetranitromethylaniline has been found suitable. 
Tetranitraniline is a very powerful explosive, 
and has a higher density than either trinitroto- 
luene or picric acid. 
The nitro-hydrocarbon high explosives used for 
the shell bursting are, in the molten state, poured 
into the cavity of the shell, in which they solidify, 
sufficient room being left for the priming charge 
and the detonating fuse. All the above nitro- 
compounds can only be obtained in a state of 
purity by re-crystallisation from various solvents. 
Fulminate of mercury has been mentioned 
several times as a detonator, or initiator of ex- 
plosion. Lead azide has been used, in conjunc- 
tion with fulminate of mercury and _ tetranitro- 
methylaniline, as a detonator for high explosives. 
It will be noticed that the majority of the high 
explosives referred to are derived from coal-tar 
products, and it is therefore evident that Mr. 
Lloyd George’s statement, “If there were a short- 
age in the coal supply for any reason, the con- 
sequences would be very calamitous,” is one 
which must be taken very seriously. 
GrorGE W. MacDona.p. 

SCIENCE IN THE SERVICE OF THE STATE. 
ODERN war is an affair of applied science— 
military, engineering, chemical, medical, 
and economic. Its successful prosecution requires 
more than an extremely high efficiency on the part 
of the officers in their professional work. Every- 
thing that chemical, physical, and engineering 
science can suggest must be pressed into service. 
The scientific men of the country have been keenly 
aware of this necessity from the beginning of the 
war, and many of them have individually done a 
great deal of important work for the Government 
and the various Services. The Royal Society has 
formed a War Committee, to which the Govern- 
ment has confided the solution of many pressing 
scientific problems arising out of the war. The 
public thanks of the country have been given to the 
Royal Society by Mr. Asquith. We note also with 
pleasure the issue, by the Council of the Chemical 
Society, of the letter (see p. 523) announcing that 
the Council has constituted itself a consultative 
body to consider, organise, and utilise all sugges- 
tions and inventions which may be communicated 
to it. 
