192 
HOW TO FORM INDIGOTIC ACID. 
gotic acid ; the residual liquor, by evapora- 
tion and adding cold water, yields an addi- 
tional quantity. 
I'he cry.stdl9 were dissolved again in hot 
water, which wasdivided into two equal por- 
tions, one of which was neutralised by carho- 
bonateof potash, and the other by carbonate 
of ammonia ; carbarotates of potash and am- 
monia were formed, and repeatedly purified 
by crystallisation. The former salt appeared 
in the form of long, yellow, semi-transparent, 
and very brilliant needles ; the latter formed 
yellow, flattened crystals. Carbazotate of 
potash possesses the property of detonating 
when heated like fulminating silver ; car- 
bazotate of ammonia is fused and volatilised 
without decomposition. It may be here 
observed, that the sparing solubility of car- 
bazotate of potash renders its acid an excellent 
test for potash. Carbazotic acid is easily 
separated from the salts by the addition of sul- 
phuric acid; its crystals are in the form 
of brilliant, yellow plates; it is extremely 
bitter, and said to be poisonous; it may be 
fused and volatilised without decomposition, 
but when exposed to a strong heat it explodes, 
leaving a residue of charcoal. 
By Liebeg’s analysis this acid contains no 
liydrogen, but, as its name implies, it is a 
compound of carbon, nitrogen, and oxygen, 
in the proportions of 15 carbon, 3 nitrogen. 
Others give different proportions, and Dumas 
found in it 1'4 per cent, of hydrogen. It 
may be formed by the action of nitric acid on 
many animal and vegetable substances, as 
silk, aloes, &c. 
To form indigotic acid, indigo in coarse 
powder was mixed with nitric acid, diluted 
with an equal weight of water ; carbonic acid 
and nitrous gas were produced, but no car- 
bazotic acid ; when effervescence had entire- 
ly ceased, it was allowed to cool; a thick, 
white precipitate fell down, which was boiled 
with oxide of lead, and filtered in order to 
separate the resin ; the clear, yellow solution 
was decomposed by sulphuric acid, and filter- 
ed at a boiling temperature. Indigotic acid 
was deposited on cooling in minute, yellowish 
white needles; by repeatedly dissolving and 
re-crystallising it finally assumed the form of 
a tult ot teatheis. 
(To be continued, ) 
INDIAN INK. — An easy and expeditious 
method of providing a substitute for Indian 
ink, is to boil parchment slips, or cuttings, 
glove leather, in water, till they form a size 
which, when cold, becomes of the consistency 
of jelly ; then having blackened an eartheny 
plate, by holding it over the flame of a can- 
dle, mix up with a camel-hair pencil the fine 
lamp-black thus obtained with some of the 
above size, while the plate is still warm. 
This black requires no grinding, and produces 
an ink of the very same colour, which works 
as freely with the pencil, and is as perfectly 
transparent as the best Indian ink. It like- 
wise possesses the advantage of furnishing 
artists with a substitute for the article, 
which may be prepared where it maybe diffi- 
cult to obtain the ink itself. 
DRAWING ON CLOTH.— A new method 
of drawing on cotton and linen cloth has 
lately been invented by Mr. John Buck, of 
12, Parker-street, Westminster, wffiich pos- 
sesses, as far as regards the portability and 
durahleness of the material, a great surperi- 
ority over every other yet devised. The 
cloth is first prepared by rubbing into it an 
adhesive composition, which unites the threads, 
and makes it as easy to draw upon as paper ; 
and after the drawing has been made, it is 
done over with a “thin pellucid liquid,” of 
varnish. It might be supposed that cloth 
thus treated would be stiff and liable to 
crack ; hut, on the contrary, it admits of 
being folded of in any shape or size, with the 
greatest ease, and without injury. A whole 
estate, or township, as the inventor observes, 
may, by this means, be introduced into 
a pocket-book.” 
SPECIFICATION OF THE PATENT GRANTED TO ELIAS CARTER, OF THE 
CITY OF EXETER, GENTLEMAN, FOR AN IMPROVED APPARATUS FOR 
REGULATING THE SUPPLY OF GAS TO THE BURNERS, AND FOR STOP- 
PING OFF THE SAME, APPLICABLE ALSO AS A COCK IN DRAWING OFF 
OR REGULATING THE FLOW OF OTHER FLUIDS. 
Sealed June 22, 1835. 
WITH AN ENGRAVING. 
To all to whomthesepresents shall come, &c. 
SiC — Noio know ye, that in compliance with 
the said proviso, I, the said Elias Carter, do 
hereby declare the nature of my said invention 
and the manner in which the same is to bg 
