CARBOLIC OR PIIENIC ACID AND ITS PROPERTIES. 
4S3 
putrid, unless they have been dried rapidly iu the sun or salted, -which necessitated a 
long and costly operation; whilst it is only necessary to immerse them for twenty-four 
hours in a solution of two per cent, of carbolic acid, and dry them in the air, to secure 
their preservation. It is probable that in a short time the blood, intestines, and other 
parts of these animals will be, by means of carbolic acid, converted into manure, and 
imported into this country. In England carbolic acid is used in the preservation of guts 
at the gut works, for keeping anatomical subjects, and the preservation of all animal 
matter. Carbolic acid is also utilized in preventing the decomposition of the prepara¬ 
tions of gelatine and albumen, used in spinning, dyeing, and calico printing. 
One of the most interesting chapters in the history of carbolic acid is certainly that 
which treats of the production of colouring materials ; they alone enter into comparison 
with those derived from aniline, and often enter into successful rivalry with them. 
Amongst the colouring matters derived from carbolic acid, the most important is, with¬ 
out fear of contradiction, picric acid. The discovery of this acid dates back to a distant 
period ; it was studied by Welter, and was called Welter’s bitter. 
My illustrious master, M. Chevreul, resumed in 1807 the study of the action of nitric' 
acid on organic matters, and showed, in an admirable paper, that picric acid was often + 
produced when organic matters were acted upon by nitric acid. M. Chevreul discovered . 
in the products of the oxidation of organic substances through nitric acid two different 
bodies, which he called amer au minima and amer au maxima , the latter being picric 
acid. This acid was again examined by Laurent in 1841. This profound chemist 
showed that the true generator of picric acid was carbolic acid; that in the action of 
nitric acid on the latter it formed three nitrogenated compounds, mononitrophenic acid, 
binitrophenic acid, trinitrophenic acid, the latter being also picric acid. 
These interesting results of Laurent would perhaps have remained for a long time 
without any commercial value if picric acid had not been applied to dyeing, in 1847, by 
M. Guinon, senior, of Lyons. Since then the use of this acid has been much extended, 
not only in producing magnificent yellows, but also, joined with indigo, in the produc¬ 
tion of ordinary greens, or of vert Lamiere with Prussian blue, so that its consumption 
may be valued at from 80 to 100,000 kilogrammes annually ; our firm alone produces 
more than 300 kilogrammes weekly; and when it is considered that 1 kilogramme of 
picric acid dyes to an intense shade 70 to 100 kilogrammes of silk, or 40 to 50 kilo¬ 
grammes of wool, the enormous quantity of textile materials dyed by this single product 
jrnay be appreciated. 
The processes used for the preparation of picric acid are still those which Laurent in¬ 
dicated in 1841; but instead of using carbolic acid, loaded with the heavy oils of tar, as 
M. Guinon had done, I sought to diminish the quantity of nitric acid, employed in mere 
waste, on the heavy oils of tar, which were then mixed with carbolic acid, and I am 
glad to say that since 1852 I have used, in the manufacture of picric acid, carbolic acid 
containing only some of its liquid homologues. In 1856, M. Bobceuf took out a patent 
in France for making picric with carbolic acid. But picric acid was then at a high price, 
and it is only since our firm has obtained carbolic acid cheap that picric acid can be pro¬ 
duced freed of all those resinous materials which prevent its purification and low price; 
in fact, owing to our pure carbolic acid, picric acid is now manufactured chemically 
pure; this product, which was sold some years since at thirty to forty francs the kilo¬ 
gramme, is now sold at the rate of ten francs. Further, I may add that to apply it iu a 
quick and economical manner it is desirable to add to the dye bath a small proportion of 
sulphuric acid; this method of manipulation, which is not generally known, is very im¬ 
portant, for it is only in this way that the textile materials can be readily dyed, and the 
baths exhausted. 
I shall now have the pleasure of calling your attention to the production of two new 
colouring substances derived from picric acid:— 
1st. Picramic acid was, in the first instance, obtained by Wohler; by making sulphate 
of iron act upon picric acid, and neutralizing with caustic barytes, a deep brown salt was 
thus produced, from which he separated the barytes by the help of sulphuric acid, and 
by these reactions M. Wohler obtained an acid to which he gave the name of nitro- 
hematic acid; but it is to M. Aime Girard that we owe the practical process by means 
of which we are able to manufacture great quantities of picramic acid. This acid im¬ 
parts to silk a beautiful series of brown tints, similar to those obtained from cit.echu. 
2nd. Isopurpurate of ammonia. It is with much pleasure that I noticed, at the Ex- 
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