December 30, 1871.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
537 
to the introduction of the aniline blues. It consists in 
dipping the silk, for several hours, in a salt of peroxide 
ot iron, when the oxide of iron beoomes fixed in the silk, 
which is washed and dipped in a slightly acid solution of 
yellow prussiate of potash. Prussian blue is thus pro¬ 
duced on the silk, which only requires washing to he 
ready for market. The only improvement made in this 
class ot dyeing has been the addition of a persalt of tin 
to the iron-salt. 
The production of Prussian blue on cotton or woollen 
fibres is effected by a curious chemical reaction. At a 
temperature of 212° F., all acids, even the organic, such 
as oxalic, citric and tartaric, as well as the acid sul¬ 
phates, possess the property of decomposing the two 
prussiates. The potassium of the cyanide combines with 
oxygen of the water and with the" organic acid. The 
• cyanogen thus liberated unites with the hydrogen of the 
water, forming prussic acid. The cyanide of Ron libe¬ 
rated unites with the fibre of the cloth, and on the latter 
being passed into a weak solution of bichromate of potash 
or bleaching powder, or if it is left exposed to the air, 
part of the protocyanide of iron is converted into sesqui- 
cyanide, and Prussian blue is produced. As salts of tin 
greatly facilitate the fixing of the prussiate on the cloth, 
chloride of tin is now generally mixed with the prussiate 
of potash. In this case prussiate of tin is produced. 
To this mixture tartaric or oxalic acid is added ; it is 
then properly thickened and printed on the calico. 
When the design is dry, the fabric is submitted to 
the action of steam, and the blue is produced on the 
fabric. It then only requires to be passed through a bath 
of bichromate of potash to develope the full depth of the 
shade. 
Ultramarine Blue is a most valuable pigment, both on 
account of its cheapness and the brilliancy of its colour. 
It is used extensively in many branches of trade—by the 
calico-printer in pigment printing, by the paper-stainer 
and manufacturer, the typographic and lithographic 
printer, by the match manufacturer, the sugar refiner, 
and by the house decorator. The value of the pigment 
depends on the fineness of the powder and the brilliancy 
of its hue. 
The greatest care and much experience are required in 
every stage of the manufacture, in purifying the sub¬ 
stances employed, in mixing, in heating at the proper 
temperature, and in grinding, washing, and drying the 
manufactured mass. Fourteen distinct operations are 
required to produce it, and it would take too much time 
at this late hour to enter into the details of these pro¬ 
cesses. I will therefore only attempt to give you a 
very rough outline of the principal points of the manu¬ 
facture. 
The proportion of materials used may be as follows:— 
White china, clay or kaolin . . .50 parts. 
Sulphate of soda.19 „ 
Sulphur.25 ,, 
Charcoal.12 „ 
Carbonate of soda.28 „ 
134 
These substances are most intimately mixed together, 
and introduced into an earthenware crucible, which is 
carefully closed and heated at a temperature of about 
500° F. for twelve hours. The temperature is then gra¬ 
dually raised till it reaches a white heat at the end of 
forty-eight hours; the fire is then removed, and the 
crucible allowed to cool gradually in the furnace. The 
mass, as taken out of the crucible, is of a beautiful 
bright green colour. It is ground, washed and dried, 
and then calcined in an open furnace to oxidize it; but 
ns the slightest excess of oxidation spoils the colour, the 
workman from time to time adds a small amount of sul¬ 
phur to the mass, by this means controlling the oxida¬ 
tion. The green mass gradually becomes blue, and is 
washed and dried, when it is ready for market. 
The colouring matter of ultramarine is not well km' vn * 
It is supposed to be a peculiar sulphate or hym dU lphite 
of soda. The solid matter itself is a dou we ’ silicate of 
soda and alumina. What is certainlr worth notice is 
that, although we arc ignorant o f the true colouring 
matter of this pigment, we fin-* its composition to be 
almost identical with that the natural Lapis lazuli, 
which, although very co^y, was employed by painters 
for many centuries. I'he following analyses will show 
the similarity of composition:— 
Lapis lazuli. Ultramarine. 
Silica .... 
. . 45-40 . 
46-60 
Alumina . 
. . 31-67 . 
23-30 
Soda .... 
. . 9-09 . 
21-46 
Potash . . . 
. . nil 
1-75 
Iron .... 
. . 0 - 52 . 
1-00 
Lime .... 
. . 3-52 . 
0-02 
Sulphuric acid . 
. . 5-89 . 
3-08 
Sulphur . . . 
. . 0-95 . 
1-68 
Chlorine . . . 
. . 0-42 . 
trace 
Water . . . 
. . 0-12 . 
nil 
Loss .... 
. . 2-42 . 
• 
1-05 
100-00 
100-00 
Artificial ultramarine was discovered by a French 
chemist and druggist, named Guimet, who kept the pro¬ 
cess of its manufacture secret for many years. 
Quercitron , Fustic , Persian Berries , Weld, Aloes, Turmeric, 
Annatto, Ilixanthine, Lakao , Tannin matters, Gall-nuts, 
Sumach, Bivi-divi, Myrobalans, Catechu . 
I shall have the pleasure of devoting the first part of 
this lecture to some of the most useful and important 
yellow substances used by dyers and calico-printers, and 
to one or two other colouring matters which, although 
scarcely commercially important, are interesting from 
a scientific point of view. 
Among the most valuable of these bodies is quercitron, 
the bark (from which the epidermis has been removed) of 
a particular species of oak, called the Quercus nigra or 
Quercus tinctoria. This tree is indigenous to the United 
States of America, and is especially found in the forests 
of Pennsylvania, Georgia, and in North and South 
Carolina. A chemist, of the name of Bancroft, first in¬ 
troduced it to the English dyers in the year 1775. The 
most esteemed qualities are those imported from Phila¬ 
delphia, New York and Baltimore. The bark, after 
being removed from the tree, is dried, and ground be¬ 
tween millstones. The value of a sample bears a direct 
ratio to the fineness of the powder, for the woody fibre 
of the bark, which contains only a small quantity of 
colouring principle, is not easily reduced to a fine 
powder. 
M. Chovreul was the first chemist w T ho examined this 
dye, and he found it to contain a peculiar tannin, which 
has since received the name of quercitannic acid, and a 
yellow colouring principle, to which he gave the name 
of quercitrin, but which has since received the name of 
querdtric acid from M. Bolley. 
M. Chevreul, by boiling quercitron bark in water, 
and allowing the aqueous solution to stand, obtained 
fine, laminated crystals, which were gradually deposited, 
and to -which ho gave the name of quercitrin. 
M. Bolley followed a better process. He treated the 
bark by alcohol, precipitated the tannin from the alco¬ 
holic solution by gelatine, evaporated the alcohol, and 
obtained the quercitrin under the form ot colourless 
crystals. These, under the influence of air or oxidizing 
agents, assume a bright yellow colour. The alkalis give 
quercitron a brownish tint, but its most characteristic 
property is to give a greenish-yellow precipitate with 
chloride of iron, and a beautiful bright yellow preci¬ 
pitate with protochloride and oxymuriate of tin. 
M. Rigaud discovered, a few years since, by boiling 
