May 31, 1673.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
957 
250 at 50° C.; and the augmentation was observed to be 
much more rapid in the higher than in the lower portions 
of this range of temperature. 
If the formula given above for the reaction be a true 
one, it follows that every atom of copper deposited on the 
silver in the state of suboxide must be compensated by an 
atom of copper dissolved from the copper plate. This was 
proved quantitatively. In a cell that had been in action 
for a week the loss of the copper plate was 0'391 gram, 
while the suboxide deposited on the silver was found to 
be equivalent to 0'398 gram of metallic copper. This 
deposit of suboxide, though it soon forms apparently a 
complete covering to the silver, does not greatly diminish 
the action; it is probably porous, besides being itself a 
conductor of electricity. In some cases it was deposited 
in crystals sufficiently large to be seen by the naked eye, 
shown by a magnifying glass to be regular octahedra. The 
internal resistance of this battery is small. 
The electrolytic power of the current was examined. 
One cell, the plates of which were about 2 inches in 
diameter, was found sufficient to decompose such metallic 
salts as the nitrates of copper, silver, or lead, copper 
sulphate or stannous chloride, in aqueous solution, when 
platinum was used for the negative electrode, and for the 
positive the same metal as existed in the salt experimented 
on. Six cells were sufficient to decompose dilute sulphuric 
acid slowly and dilute hydrochloric acid pretty quickly, 
copper electrodes being employed. 
The theoretical interest of this battery lies mainly in 
the fact that it differs essentially from every other galvanic 
arrangement, inasmuch as the binary compound in solu¬ 
tion is incapable of being decomposed either by the posi¬ 
tive metal alone or by the two metals in conjunction ; it 
cannot serve, in fact, as the liquid element of the circuit 
without the presence of another body ready to combine 
with one of its constituents when set free. Grove’s gas- 
battery is essentially different if the oxygen and hydrogen 
condensed on the platinum plates play the part of the two 
metals ; but it closely resembles it if hydrogen acts the 
part of the positive and platinum that of the negative 
metal; the dilute sulphuric acid, a hydrogen compound, 
will then be decomposed on account of the simultaneous 
presence of the oxygen, which can combine with the libe¬ 
rated hydrogen. Viewed in this manner, Grove’s gas- 
battery is only a special case of the general reaction 
described in a previous paper; and the formula will be :— 
Before contact, mPt -j- 0 -f- II.-, S0 4 -j- n. H ; after contact, 
0iPt + H 2 0 + H 2 S0 4 + (n - 2)H. 
The practical interest of the present arrangement lies in 
the fact that it is an approximation towards a constant 
air-battery. Should it ever come into use elsewhere than 
on the lecture table, it will probably be in the form of a 
combination of zinc and copper, with an aerated solution 
of zinc chloride ; for that arrangement has an electro¬ 
motive force six times that of the arrangement more par¬ 
ticularly studied, and about three-quarters that of a 
Daniell’s cell. The numbers representing the difference 
of potential between the two metals, which were actually 
obtained by means of an electrometer belonging to Sir 
William Thomson, weie — 
Silver and copper with deoxygenized 
copper nitrate ... ... ... 4 
Silver and copper with oxygenized cop¬ 
per nitrate ... ... ... ... 8 to 11 
Copper and zinc with chloride of zinc 62 
„ „ water ... ... 68 
„ „ Daniell’s cell ... 83 
Chloride of zinc is preferred to the sulphate, as it offers 
less internal resistance, and a solution of 20 per cent, is, 
on the authority of Mr. Herbert MacLeod, recommended 
as about the best conductor. A single cell of this descrip¬ 
tion is capable of decomposing dilute sulphuric or hydro¬ 
chloric acid, when copper electrodes are employed. The 
two metals might be arranged as in a Daniell’s battery ; 
the zinc would of course require no amalgamation, and 
the whole might be left for weeks or months without any 
attention. The oxide of zinc produced generally falls to 
the bottom of the vessel, and may be separated whenever 
it is thought desirable. 
The power is thus obtained at a minimum of expense, 
for the oxygen which combines with the zinc costs nothing. 
Such a battery would appear to be specially adapted to 
cases where the galvanic current has to be frequently 
broken, as in telegraphy; for at each period of rest it 
renews its strength by the absorption or diffusion of more 
oxygen from the air. 
THE MANUFACTURE OF PEPSIN * 
BY E. KOTHEE. 
With the important discovery of Mr. E. Scheffer, of 
Louisville, Ky., a new era was developed in the manufac¬ 
turing interests of pepsin. The multitude of uncertain 
and mostly worthless preparations, erroneously called 
pepsin, have been swept from the market by the bond fide 
article, which alone merits the title, and is, in truth, the 
coveted desideratum, pepsin. This real, active, definite, 
and always reliable pepsin is most abundantly, easily, and 
expeditiously obtained by the process of Mr. Scheffer, 
which consists in precipitating it from its acidulated 
aqueous solution by saturation with chloride of sodium. 
The history of pepsin will record an entire revolution 
through the agency of this simple method. The commer¬ 
cial interest will suffer a thorough change, as henceforth 
the exorbitant price of a comparatively worthless sub¬ 
stance will be reduced to a very moderate rate, and then 
purchase a very superior article. 
In the preparation of this substance the pharmacist 
ordinarily imagines an exceedingly unpleasant operation. 
But the sooner he disabuses his mind of this nauseous 
idea the greater will be the advantage to him. The pro¬ 
cess, however, is mere pastime, when compared to many 
less dreaded duties comprised in the routine of pharmacy. 
Pigs’ stomachs are the best sources of pepsin, and the 
yield of such a peculiar principle, exerting such a vast 
digestive power, is comparatively enormous, if the proper 
means are employed to secure it. The first consideration 
which requires attention is, that the stomachs must be 
fresh. The contents are then immediately removed, and 
the stomachs well cleaned by a judicious use of fresh 
water, so as not to wa»ste the mucous membrane in which 
the digestive principle seems to reside. The second step 
consists in cutting them into moderately thin shreds by 
means of scissors. This done, they are macerated for two 
days in a large volume of acidulated Water,—the more 
the better. However, one gallon of water, acidulated 
with half an ounce of muriatic acid, is ample for one 
stomach. At the end of this time the acid liquor is 
poured off, and the stomachs are again macerated for two 
days, with a similar quantity of acidulated water. This 
operation of macerating the stomachs can be performed 
three times with advantage, and even a fourth maceration 
will repay the effort. The liquids obtained from each 
maceration are immediately treated with about one-fourth 
their weight of common salt, and the precipitated pepsin, 
which accumulates in curdy flakes upon the surface of the 
liquid, is skimmed off with a ladle, collected on a muslin 
strainer and strongly pressed, to separate the most of the 
adhering water. The cake of yet moist pepsin is. then 
mixed with a weighed quantity of milk sugar, the. mixture 
spread out to dry, then weighed, and sufficient milk sugar 
added to make the final weight of the mixture equal to 
ten times the weight of the real pepsin contained in it, 
which is determined from the difference between the 
weight of the dried residue and the known quantity of 
milk sugar at first added. A source of error may, how¬ 
ever, occur here, and the finished preparation be under 
* From the Chicago Pharmacist for March. 
