22 
chemicals yielded probably 2,000 other compounds. In coal tar itself com- 
paratively few of these substances existed, but compound products 
could be multiplied very largely. If it had not been for the abundance of 
high explosives, which were for the most part the produce of coal tar, we 
should never have won the war. The most interesting product from the 
explosive point of view had been trinitrotoluol. All coal tar oils 
would burn and give out a great amount of heat, as for instance 
benzol, which had been largely used during the war for driving motor cars, 
owing to the shortage of petrol. Coal tar oil was also used for driving fast 
cruisers. Some of these oils had been very useful in driving heavy traction 
engines. The Lecturer spoke of an acid derived from coal tar which was a 
great preventive of rats in dug-outs, and of the discovery of a new 
antiseptic, which caused wounds to heal with astonishing rapidity. He gave 
details of the chemical composition, starting off with toluol, which made the 
curious compound saccharine. Five hundred times as sweet as sugar, it was 
absolutely a drug, but he believed the medical profession as a rule were of 
opinion that it was not a harmful thing to take. Ali drugs, however, wanted 
treating with a certain amount of caution. After a reference to salvarsan, 
which is a benzine derivative with two molecules of arsenic, the 
Lecturer passed on to deal with aniline dyes. The first dye dis- 
covered of any importance was majenta. This was the point from which 
it became easy to make a whole series of dyes by introducing various com- 
pounds. A reference to sulphur, or vat-dyes, from which khaki is dyed, was 
not the least interesting part of the lecture.’ It had been found that when 
these dyes were treated in an alkaline solution a thin, colourless compound was 
formed, and when an article, whether cotton or woollen, was inserted in it 
and then brought out again, it apparently possessed no colour, but on being 
exposed to the air, it assumed on oxidisation its original colour, and this was 
done with khaki. Coal tar dyes in pigments had formed a very prominent 
feature in camouflage. Photography had played an enormous part in the war, 
and most modern developers were of coal tar origin. The Lecturer also had 
something to say about gas and tear shells, which were the products of coal 
tar. He generally shewed that those who have had anything to do with coal 
tar or coal tar products during the war have at anyrate ‘‘ done their bit.” 
The second Lecture was one on ‘ Leather;’”? and was announced on the 
SylHabus to have been delivered by Mr. C. I. Smith, late of the Leather 
Department, Leeds University. Unfortunately this gentleman was unable to 
fulfil his engagement, and the Chairman of the Section, Mr. J. Bairstow, 
J.P., F.C.S., at very short notice prepared an original paper on the subject 
to fill the gap. The Lecturer declared that the origin of tanning, the art by 
which hides are converted into leather, must ever remain shrouded in 
obscurity. After Biblical, classical and archeological references, the 
Lecturer said that one difficulty in ascertaining the probable age of leather 
was that in Latin, Greek and Hebrew the terms leather and skin were used 
indiscriminately. In England foolish enactments so hampered the tanners 
that for nearly 300 years the trade was at a standstill. In 1830 the tax on 
leather was abolished. Tanners of 80 years ago had limited capital. a dread 
of improvements, 2nd were ignorant of chemistry. To-day the contrary was 
the case, and in Professor H. R. Proctor, England possessed perhaps the 
greatest expert in the chemistry of leather who ever lived. Mr. Bairstow 
dealt with leather supplies from various parts of the .world, the extreme 
importance of the water supply, vegetable tanning materials and _ their 
extraction, sole and light leather tanning, and dyeing: Describing the 
mineral tannages. he said the most important was that involving the use of 
the salts of chromium. Though of only very recent origin, the process had 
already become a yery serious rival to the vegetable tannages, and even in 
some cases had replaced them to some extent. He also explained the alum, 
oil, and Syntan systems, the last mentioned of which was originally in 
German, but now in British hands. In 1910 leather imports into this country 
reached a value of £16,000,000, and exports £10,000,000. 
