i 882.] 
Analyses of Books. 
545 
to Dr. Weyl, 350,000 tons, of which the larger part is obtained 
in England, 50,000 tons in France, 15,000 in Belgium, and half 
that quantity in Holland. For Germany Dr. Weyl gives no 
figures, but, according to the “ Chemische Industrie,” the annual 
quantity there distilled is 37,500 tons. According to Mills, as 
far back as 1874 the weight of coal consumed in the United 
Kingdom, for the manufacture of gas, is 10,000,000 tons, which 
would represent a yearly production of about 450,000 tons 
of tar. 
The production of tar at the gas-works fluctuates according to 
the quality of coal employed, and not less according to the tem- 
perature at which the retorts are worked. According to a table 
here inserted the yield ranges from 4 per cent of the coal up to 
6, the quality also being far from uniform. 
In connection with this subject "our attention is drawn to the 
prospeCt of utilising the very large quantity both of tar and 
ammonia which at present are wasted in the conversion of coal 
into coke for metallurgical purposes. Attempts, it appears, have 
been made in this direction since 1768. Dr. Lunge, whilst no- 
ticing several of the processes proposed, does not commit himself 
to any statement as to their remunerative character. He 
considers, however, Dr. Angus Smith’s report on the modi- 
fied Knab process, as carried out at Bessages, as rather too 
favourable. 
A notice is also given of the proposal to obtain some of the 
most important constituents of coal-tar by decomposing the 
heavier oils (at present of little use) of the petroleum and paraf- 
fin oil-refineries. Here there is room to hope for results which 
may emancipate the tar-distiller and the dye-manufaCturer from 
their present dependence upon the gas-companies. 
In the second chapter Dr. Lunge treats of the properties of 
coal-tar and its constituents, of which he enumerates no fewer 
than 1 14, arranged under the heads of hydrocarbons, oxygenised 
compounds, sulphuretted compounds, and nitrogenised com- 
pounds. We find the remark that not a few authors of standing 
— such as Bolley, Wurtz, Girard and Delaire, &c. — have stated 
the specific gravity of coal-tar as being only equal to, or even 
below, that of water. In reality it ranges from i-io to 1 * 20 . 
The next chapter is devoted to the applications of coal-tar 
without distillation, such as for gas-making, for heating, for pre- 
serving stones, brickwork, metals, and wood, as an antiseptic (it 
has been used, in conjunction with lime and magnesium chloride, 
for the treatment of sewage), for the production of lamp-black 
and of printing inks. 
In the fourth chapter we find an account of the first distillation 
of coal-tar, embracing dehydration, previous purification, the 
construction and setting of stills, condensing apparatus, filling 
and firing the stills, the principles and different systems of frac- 
tional distillation, with the separation of ammoniacal liquors, 
