166 
ON THE PREPARATION OF CHLORO— CHROMIC ACID. 
6. CYANILIC ACID.-If the yellow pow- 
der which is obtained from the decomposition 
of sulpho-cyanodide of potassium by chlo- 
rine, and which is mixed with chloride of 
potassium, be well washed and boiled with 
nitric acid, it dissolves gradually, and the 
liquid on cooling deposits colourless and 
transparent octahedrons with a square bass, 
which consist of pure cyanilic acid. To 
accelerate the decomposition of the salt of po- 
tash, it is advantageous to add twice its weight 
of common salt. At first chloride of sul- 
phur distils over, and latterly long needles 
of chloride of cyanogen are deposited in the 
neck of the retort. The yellow residue is 
carefully washed and dissolved in nitric acid, 
'i he new acid is more easily soluble in cold 
water than cyanuric acid. 1 he crystals 
contain water which they lose by heating, to 
the amount of 21 percent. Its composition 
is. Carbon 28T85 Azote 32’640 Oxygen 36*874 
Hydrogen 2*300 Total 100 000 which Liebig 
considers equivalent to 6 atoms of each. To 
determine the atomic weight of the acid, a 
portion was neutralized by ammonia, and 
precipitated by nitrate of silver. 93*3 cya- 
nilate of silver afforded 54*5 chloride of 
diver. 58*2 after being exposed to a red 
heat, left 26*4 silver. Hence, the atomic 
weight of the acid is 16*25 or double that of 
cyanuric acid, which it very much resembles 
in its propel ties. Cyanilic acid is converted 
into cyanuric acid by dissolving it in sul- 
phuric acid, adding water and crystallizing. 
All the cyanurates and cyanilites are 
decomposed when they are crystallized in an 
acid liquor; the bases remain in solution, 
and the crystals which are formed are cya- 
nuric acid or cyanilic acid. In precipitating 
the nitrate of silver by cyaniiate of potash, 
Liebig obtained a substance which had pre- 
cisely the same composition as cyanurate of 
silver, from which it would appear that the 
alkalies can change cyanilic into cyanuric 
acid. 
7. CHLORIDE OF CYANOGEN.— 
During the decomposition ofsul pho-cyanodide 
of potassium by chlorine, besides chloride of 
sulphur, chloride of cyanogen distils over, 
which may be separated from the former by 
sublimation in a vessel through which a cur- 
rent of dry chlorine is passed. Chlorine of 
cyanogen thus obtained consists of brilliant 
needlees, possessing a strong disagreeable 
odour. To determine the quantity of chlorine, 
the salt was dissolved in alcohol, ammonia 
was added, and the liquid boiled with a 
great quantity of water until all the spirit 
was volatilized. 
Nitric acid was then added in excess, and 
precipitation produced by nitrate of silver. 
The composition ofthe chloride of cyanogen 
was in this manner determined to be Chlo- 
rine 57*03 Cyanogen 42*97 Total 100 000 or 
equal atoms of chlorine and cyanogen. Chlo- 
ride of cyanogen dissolves in absolute alco- 
hol without alteration. 
8. C YAN AMIDE.-If chloride of cya- 
nogen is moistened with ammonia, and 
gentle heated, it loses i^s crystalline form, 
and is reduced to a white powder, which is 
slightly soluble in boiling water, and is pre- 
cipitated on cooling in flocks. The same 
substance is obtained by passing ammoniacal 
gas over chloride of cyanogen in powder. 
A white powder is the result which may be 
purified by washing. The chlorine which it 
contains is not removed by ammonia. Potash 
disengages ammonia from cyanamide. Liebig 
considers it analogous in its composition to 
oxamide, and to a chloride of cyanogen. 
URIC ACID. — Liebig states that he was 
encouraged to make the preceding researches 
in the hope of finding anew combination 
w'hich would throw some light upon the 
composition of uric acid. Liebig considers 
the determination of Dr. Kndweiss, with 
respect to the proportion of azote, to be nearer 
the truth than any other. He himself makes 
the composition of uric acid : 
Calculated. Experiment. 
Carbon 36.11 - 36*073 
Azote 33*36 - 33*361 
Oxygen 27*19 - 28*126 
Hydrogen 2*34 - 2*441 
METHOD OF PROCURING OXIDE 
OF CHROMIUM IN CRYSTALS.— 
Wohler has found that the green oxide of 
chromium, which is well known as a green 
powder, may be obtained in the state 
of crystals by passing the vapour of chloro- 
chromic acid through a red hot glass 
tube.* A mixture of chlorine and oxygen is 
formed, and the crystals of oxide are depo- 
sited in the tube. Thus prepared, it is not 
green but black, possessing the metallic lus- 
tre, and has the same form as native peroxide 
of iron, (fer oli^iste or ihombohedral iron 
ore) which he considers a proof of the ismor- 
phism of these two oxides. 4'he spec, crav, 
in the crystallized state differs little from that 
of peroxide of iron, being 5*21. 
It scratches rock crystal, hyacinth, and 
cuts glass. In the crystallized state it is there- 
fore as hard as corundum, which, with the ex- 
ception of the diamond and rhodium, is the 
hardest of known substances. Chloro-chro- 
mic acid was discovered by Professor Thomson 
in 1824, and is prepared by distilling in a 
glass retort 500 gr. sulphuric acid, with 
190 gr. dry bichromate of potash, and 225 
gr. of decripitated common salt. According 
to Dr. Thomson, it consists of one atom 
chlorine, and one atom chromic acid. Rose 
considers it a combination of two atoms 
chromic acid and one perchloride of chro- 
mium. Wohler prepares it by distilling ten 
parts common salt, 16*9 neutral chromate of 
potash, and thirty parts of concentrated sul- 
phuric acid. — Record General Science, 1835. 
ALCOHOL AND ITS COMPOUNDS.! 
1. Aldehyde, (from alcohol dehydrogenatus,) 
may be prepared bypassing vapour of ether 
through a long glass tube filled with pieces 
of glass heated to redness. Theproduct, accord- 
ing to Liebig, is aldehyde, an inflammable gas, 
and water, with a slight deposit of charcoal. 
By passing this product into a vessel, half 
* Ann. de Chim. Ivii. 105. 
+ Ann. de Chiin. et de Phys. lix. 289. 
