June 21, 1873.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
1011 
G. trifoliata. These roots possess emetic and cathartic 
properties. As an emetic they are in no way superior 
to ipecacuanha, although in case of a scarcity of the 
latter drug, they might in some measure replace it. 
Four articles have been dismissed from the se¬ 
condary list—aletris, angelica, arum, gossypii radix. 
Aletris is th q Aletris farinosa, which has been used as 
an uterine tonic. Angelica is the same species that 
was formerly officinal in this country. Arum is the 
A. triphyllum, known in America as dragon-root or 
Indian turnip. Like most of the Aracece, it is very 
acrid when fresh, and loses its properties when 
heated or dried. It was one of those unstable reme¬ 
dies which are well weeded out of a Pharmacopoeia. 
Gossypii radix has been replaced by gossypii radicis 
cortex, which now figures in the primary list. 
NEW METHOD OF ESTIMATING NITRIC, 
CHLORIC, AND IODIC ACIDS. 
In the current number of the Journal of the Che¬ 
mical Society , page 541, appears a paper on a new 
method of estimating nitric, chloric, and iodic acids, 
by T. E. Thorpe, Esq., F.R.S.E. The method devised 
by Professor Thorpe is based on a reaction noticed 
by Messrs. Gladstone and Tribe, an account of which 
appeared in a recent number of this journal. When 
zinc-foil is placed in a solution of copper sulphate, its 
surface, after a time, becomes coated with a spongy 
deposit of copper. The zinc thus coated causes rapid 
evolution of small quantities of hydrogen when placed 
in pure distilled water, especially if gently heated. 
Professor Thorpe has found that if nitre be placed in 
the water surrounding the two metals no hydrogen is 
evolved, but a distinct smell of ammonia is perceived, 
the water acquiring a permanent alkaline reaction 
from the formation of potassium hydroxide. This 
reaction is represented in the following equation— 
8H 2 + 2KN0 3 =2NH 3 +2KH0 + 4H 2 0 
The ammonia evolved from a given quantity of pure 
nitre was estimated by leading it into dilute hydro¬ 
chloric acid, precipitating as platinum-ammonium 
chloride, drying and weighing. The following results 
show that the conversion of the nitrogen into ammo¬ 
nia is complete— 
(1) 0-5090 grni. KN0 3 gave 
1-0498 grm. PtCl 4 2NH 4 C1, and 0-0301 gram. Pt, 
equivalent to 0*50908 grm. KN0 3 
(2) 0*4183 grm. KN0 3 gave 
0*9208 grm. PtCl 4 2NH 4 C1, and 0*0013 grm. Pt, 
equivalent to 0*4188 grm. KN0 3 
In other experiments the following numbers were 
obtained— 
KN0 3 used. KN0 3 found. 
0-0474 gram. (1) 0*0476 gram. 
- (2) 0-0473 „ 
- (3) 0-0487 „ 
- (4) 0-0469 „ 
The presence of alkaline chlorides and sulphates is 
without influence on the result. Calcium nitrate, 
lead nitrate , and therefore in all probability the 
nitrates of silver, mercury, copper, thallium, and in 
fact of all metals precipitated by zinc, are similarly 
decomposed, the zinc nitrate which is formed being 
afterwards reduced. Of all the nitrates experimented 
upon, the most difficult of reduction appears to be 
ammonium nitrate. The discordances appear to 
depend upon differences in the strength of the solu¬ 
tion and the amounts of zinc and copper taken. If 
the solution is too strong, nitrogen dioxide is 
evolved, and if the amount of zinc and copper be 
insufficient the reduction is incomplete. With pre¬ 
cautions ascertained by experiment, however, the 
conversion of the nitric acid into ammonia is com¬ 
plete in the case of ammonium nitrate. 
The mixture of zinc and copper appears to have 
very slight action upon urea. A minute quantity of 
ammonia found was referred to a trace of ammonium 
salt present in the urea, arising from the mode of 
its formation, or more probably being produced by 
decomposition of the urea from long-continued boil¬ 
ing with water. 
Professor Thorpe believes that this reaction might 
be usefully applied to the determination of nitrates 
when present in drinking waters, and suggests a 
modus operandi, which, omitting certain details, is. as 
follows. The weighed residue in the platinum dish 
obtained in the determination of the total soluble 
matter in the water is treated with 10 or 12 c. c. of 
water, to which a small piece of previously ignited 
lime about the size of a hemp-seed is added, and the 
liquid is gently boiled until about 4 or 5 c. c. only 
remain. The primary object in adding the lime is to 
facilitate the evolution of the ammonia. Three or 
four grams of thin sheet zinc previously cleaned by 
a little dilute acid, and cut into small pieces, are 
placed in a flask, which has a capacity of 100 c. c. 
The zinc is covered with a moderately concentrated 
solution of copper sulphate, which is allowed to act 
until a thick dark brown spongy covering of copper 
is precipitated. The metals are repeatedly washed 
by decantation with cold water, care being taken to 
detach the copper particles as slightly *is possible 
from the zinc, and lastly drained. The nitrate solu¬ 
tion and the rinsings from the platinum dish are 
transferred to the flask until the liquid therein 
amounts to 25 or 30 c. c. A caoutchouc stopper 
pierced with two holes and carrying a funnel-tube 
provided with a well-fitting glass stopcock, and a de¬ 
livery-tube bent twice at right angles, is then in¬ 
serted. The delivery-tube terminates in a test-tube, 
also provided with a caoutchouc stopper, into which 
is fitted an exit-tube containing fragments, of glass 
moistened with very dilute hydrochloric acid. One 
drop of pure dilute hydrochloric acid is placed in the 
test-tube, which is cooled by immersion in distilled 
water, and the distillation is commenced. The liquid 
in the flask is boiled away, nearly to dryness ; boil¬ 
ing distilled water is added by means of the funnel, 
and the distillation continued. This process is re¬ 
peated till the test-tube contains about 40 c. c. of 
water, the contents of the exit-tube are rinsed into 
the test-tube, and the latter, replaced by a second 
tube of precisely the same size. Another distillate 
of 40 c. c. is collected, the. glass fragments again 
rinsed and a third tube substituted. The contents oj. 
the three tubes are diluted till, they measure. 50 c. c., 
and the amounts of ammonia contained in each 
are then estimated in the usual way by Nesslers 
solution. 
Direct experiments made with the view of testing 
this method of determining nitrates in water show 
that it is thoroughly trustworthy. In each case all 
the ammonia was contained in the first 40 c. c. of 
distillate. 
The chief advantage claimed for this process over 
the aluminium, or the zinc and iron, process, is that 
