July 2, 1870.] 
THE PHARMACEUTICAL JOURNAL. 
15 
Bunsen gas flame without collapsing. The solution 
of arsenic introduced into A gives, by the action of 
the zinc and acid, arsenuretted hydrogen:— 
As 2 0 3 -f-.rZn -f- a’H 2 S0 4 . 
—a? Zn S0 4 -f- 3 Ho O -j- 2 As H 3 -)- (x —0)U 2 . 
[,t—any indefinite number of atoms.) 
The mixture of hydrogen and arsenuretted hydro¬ 
gen escapes through C, which is heated to redness 
after the air has all been driven out. The elemen¬ 
tary arsenic is then deposited as a brown or black 
sliining stain on the glass, just beyond the lamp, 
whilst the hydrogen passes on and escapes. 
For estimating the amount of pure white arsenic 
in any of its preparations, the Pharmacopoeia indi¬ 
cates that 4 decigrams of it dissolved with about 
twice its weight of bicarbonate of soda, discharge the 
colour of 80 *8 cubic centimetres of the volumetric 
solution of iodine. 
White arsenic, when treated with iodine in the 
presence of water, gives rise to hydriodic acid and 
arsenic anhydride; both these are colourless, and 
therefore the brown colour of the iodine disappears. 
As 2 0 3 +20H 2 + 2I 2 =As 2 0 5 +4HI. 
One molecule of white arsenic (198 grams), ac¬ 
cording to this equation, will reduce 4 atoms (127 x 4 
=508 grams) of iodine. Now 508 grams iodine are con¬ 
tained in 40,000 cub. centims. of the solution (for in 
making it 12 - 7 grams are dissolved in 1000 of the 
liquid), so that 40,000 cc. would be the quantity de¬ 
colorized by 1 gram-molecule of white arsenic. Such 
an amount would never be used in an experiment, 
but a simple calculation shows that the quantities in¬ 
dicated in the B. P. are in the same proportion to 
each other. For 
Grams of As 2 0 3 . Cc. of Yol. Sol. of I. Gram As 2 0 3 . Yol. Sol. I. 
198 : 40,000 as ’4* : 80‘8 
The best antidote to white arsenic is freshly made 
ferric hydrate; it gives rise to an insoluble ferrous 
arseniate. 
Arsenic Acid. —The substance generally known by 
this name is again the anhydride, not the true acid. 
It is prepared by boiling white arsenic with nitric 
acid, and evaporating to dryness; the residue is a 
white powder, the anhydride, As 2 O s . By dissolving 
this in water, and concentrating the solution, the 
acid, H 3 As 0 4 , is obtained in deliquescent crystals. 
Arsenic acid and its salts are distinguished from 
arsenites, and also from phosphates, by giving a red 
precipitate with nitrate of silver, Ag 3 As0 4 . 
Soda: Arsenias. Arseniate of Soda, Na 2 HAs0 4 , 
7 H 2 O.—Arsenious acid, nitrate of soda, and dry 
carbonate of soda, are thoroughly mixed, and then 
fused at a red heat in a crucible. When the effer¬ 
vescence (caused by the escape of N 2 O s and C 0 2 ) 
has ceased, the fused salt is poured out upon a stone. 
As soon as it has solidified, the mass is boiled in 
water and the liquid set by to crystallize. The in¬ 
gredients react in the following manner:— 
198 85x2=170 106 
As 2 O a + 2NaNO. -f Na 2 C0 3 
= Na 4 Asj0 7 + N 2 0 3 + C0 2 . 
Sodium pyro-arseniute. 
It will be seen that the proportions of the ingre¬ 
dients ordered in the B.P. are nearly identical with 
those required theoretically, as shown in the equa¬ 
tion ; the carbonate of soda only being in trilling 
excess. 
Parts of As 2 0 3 . NaN0 3 , 
Theory . . . 198 170 
Being nearly =: 10 8| 
B.P.10 8| 
Na 2 C0 3 
100 
Ki 
Arseniate of soda crystallizes sometimes with 12 in¬ 
stead of 7 molecules of water; the tests of the B.P. 
must, therefore, be made use of to identify the offi¬ 
cial salt. At 300° F. it loses the whole of its water 
of crystallization, amounting to 40’38 per cent. 1 
gram of the residue, that is, of anhydrous arseniate 
of sodium, mixed with 5‘3 cubic centimetres of volu¬ 
metric soda (which converts it into trisodic arseniate, 
Na 3 As0 4 ), continues to give a precipitate of arseni¬ 
ate of silver with volumetric nitrate of silver, till 
16T3 cubic centimetres of the latter have been 
added. 
Ferri Arsenias. Arseniate of Iron .—Made by 
mixing together solutions of arseniate and acetate of 
soda and sulphate of iron. The arseniate and sul¬ 
phate of iron would alone give rise to the production 
of an acid arseniate of iron, which would not be 
precipitated, probably thus :— 
4Na 2 HAs0 4 -f 4FeS0 4 
= 4Na 2 S0 4 + Fe 3 2As0 4 + Fe"H 4 2As0 4 . 
But the addition of the acetate of soda remedies 
tills, and the whole of the iron is precipitated as 
arseniate. 
2Na 2 HAs0 4 + 3FeS0 4 + 2NaC 2 H 3 0 2 
= 3Na 2 S0 4 -+- Fe 3 2As0 4 + 2HC 2 H 3 0 2 . 
[§ A small quantity boiled with excess of caustic 
soda and filtered, gives, when exactly neutralized by 
nitric acid, a brick-red precipitate on the addition of 
solution of nitrate of silver.] This distinguishes it 
from the phosphate, which it closely resembles in 
appearance. 
Acidum Benzoicum. Benzoic Acid. — May be 
prepared,— 
1. By mixing benzoin with sand, and heating cau¬ 
tiously ; the benzoic acid rises and condenses in the 
cool cover of the pot in crystals. 
2. By boiling benzoin with half its weight of 
slaked lime, which forms, with the acid present, 
benzoate of lime, filtering, concentrating, and adding 
hydrochloric acid. On cooling, the acid crystallizes. 
3. By boiling liippurate of lime, obtained by add¬ 
ing lime to cows’ and horses’ mine, with hydro¬ 
chloric acid. 
Hippuric acid, or benzo-glycocine. Water. 
HC 2 (C 7 H 5 0)H 3 N0 2 + h 2 o 
Glycocine. Benzoic acid. 
= CjHjNOj + HC 7 H 5 0 2 . 
4. By oxidizing naphthaline with nitric acid, 
Ci 0 H 8 + 40 2 
Naphthaline. Oxygen, 
from the nitric acid. 
= HoC 8 H 4 0 4 
Phthalic acid. 
-}- U 2 C 2 0 4 . 
Oxalic acid. 
and converting the phthalic acid into a salt of lime, 
and heating this pretty strongly with hydrate of 
lime. The phthalate of lime is converted into ben¬ 
zoate and carbonate. 
2CaC 8 H 4 G 4 
Phthalate of lime. 
= Ca2C 7 H 5 0 2 
Benzcate. 
-f Ca2HO 
Hydrate of lime. 
-f- CaC0 3 . 
Carbonate. 
5. By exposing essential oil of almonds (benzoic 
aldehyde or hydride of benzoyl) to the air, it absorbs 
oxygen. 
