40 PRESIDENT’S ADDRESS. 
organic compounds, can be built up. Whether its cheapness 
will be taken advantage of for such purposes is at present 
doubtful. 
A solution of acetylene in acetone appears to be less liable 
to explode than liquid acetylene ; and, further, for the same 
unit of pressure on the cylinder, a larger volume of acetylene 
can be stored, 7.e., a solution in acetone contains more acety- 
lene per unit of pressure than one of liquid acetylene. 
There is no advantage in using liquid acetylene for 
transport, for ] kilogramme (2°2 lb.) of calcium carbide only 
occupies the volume of ‘45 litre, and yields °3 cubic metre 
of acetylene, which, when liquefied, occupies twice the 
volume of the carbide. To light a railway carriage with 
200-candle power for ten hours requires about 15 cubic 
metres of coal gas, about 8 of oil gas, but only 1°5 cubic 
metres of acetylene. 
ARTIFICIAL INDIGO. 
Alizarin, the bright red dye from madder, has now been 
made artificially from anthracene (formerly a waste pro- 
duct from coal tar) for some years, and it has practically 
superseded the use of madder for dyeing Turkey red, at a 
saving to Hnglish calico printers and dyers of, perhaps, 
£2,000,000 or £3,000,000 per annum. 
Various methods for making indigo artificially have also 
been worked out, and although they are successful enough 
as laboratory experiments, they have not hitherto been 
successful from a commercial poimt of view, because the 
synthesised product costs more than the natural indigo. 
Lately, however, the Badische Anilin und Soda Fabrik have 
offered in the market an indigo which is said to be a coal- 
tar derivative. It is admitted to bea better dye, but the 
price is higher than that for the best natural indigo. 
No details are given as to the method of manufacture ; 
but, if it really be an artificial product, we may in time 
expect it to be sold at a lower rate than natural indigo, 
when indigo-planting may become a thing of the past, just 
