September 10, 1870 .] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
217 
the general results are known to us, but of which the 
particulars are, I may say, in the main almost completely 
unknown. As to the processes by which these products 
are formed, it is as well to say that we do not know them. 
We know a little here and there about them, but it is 
nothing compared to our ignorance; therefore the re¬ 
semblance is the more striking, and if -we were to believe 
in the contagiousness of chemical action as applied to the 
case of the assimilation of sugar by a ferment, and say 
the ferment gives off alcohol and carbonic acid, and that 
sugar is also resolved into alcohol and carbonic acid, we 
should really be describing in its general features a pro¬ 
cess analogous to that which I have just now mentioned; 
such a general analogy would be readily admitted by those 
who go into the particulars of the process, but I think it is 
of particular importance to have in addition to it some¬ 
thing more practically useful to guide us in understanding 
chemical reactions. For that purpose I will take one or 
two chemical reactions of an exceedingly common kind. 
For instance, I will again take that chromic acid solution 
which I just now employed. Here you see is the green 
residue which I told you would be produced; I again 
take some of this chromic solution, throw some of it into 
water in this jar, so as to visibly tinge the water red ; I 
will slightly acidulate the liquid by oil of vitriol, and I 
will then pom’ into the mixture (which I will describe as 
chromic acid dissolved in water, for the potash which was 
present is taken away from the compound by the sulphuric 
acid), a substance w T hich I will merely describe as being- 
greedy of oxygen, sulphurous acid. If Liebig’s theory 
of contagious action were generally true in chemical 
action, you would no doubt expect that this sulphurous 
acid, in taking up oxygen, would make the chromic acid 
also take up oxygen. It is quite possible for the chromic 
acid to do so, for that blue substance which we had in 
this jar at first was nothing but chromic acid with 
oxygen added to it. But instead of this, we shall have 
at once a reduction of the chromic acid to deep green, 
which I dare say appears to you almost black. It is 
precisely the same thing as that pale, dirty green which 
you saw before, but in its concentrated state. There is 
no oxygen taken up by the chromic acid, but it at 
once loses oxygen. This sulphurous acid wanted to 
combine with oxygen, and it tore away at once some 
of .the oxygen from the chromic acid, and there -was in 
this chromic acid a process, not similar to that which 
the sulphurous acid underwent, but a process precisely 
opposite to it—one combined with oxygen while the 
other lost oxygen,—and if you examined the liquid, you 
would find that the sulphurous acid which took part in 
the process, and has taken up oxygen, is now T in the 
form of sulphuric acid. Again, I have here some granu¬ 
lated zinc, which will very easily evolve hydrogen, par¬ 
ticularly wdien its activity is stimulated by throwing a 
little copper vitriol on to it. After adding a little water, 
I will throw in a little oil of vitriol, so as to get an evo¬ 
lution of gas. Then I have here a solution which I 
think must look black to you, except at the edges, which 
is a solution of a beautiful salt called permanganate. 
It is used for deodorizing certain fetid waters, and I 
might compare it to the chromate I was using just now. 
It consists of an acid of the metal manganese. If I 
throw some of that into the mixture which I have just 
prepared, and leave it for a short time, and then ex¬ 
amine it, we shall find that, instead of being induced 
to give off hydrogen like the other body, which is doing 
so vigorously, we shall find it will do the opposite, and 
will combine with hydrogen; and the colour -which 
belongs to it, and which can be recognized so easily, 
will disappear, because hydrogen will be taken up by 
its oxygen, and it will be reduced and brought down 
to a substance containing comparatively little oxygen. 
There, again, as in the previous case of the chromic 
acid, we find that there is a kind of chemical polarity 
in the general mode of action, that the one substance 
acted upon does precisely the opposite of the other. 
There is no tendency in this case to do the same thing, 
but the two substances acting upon one another do pre¬ 
cisely the opposite, the one taking up what the other 
loses. Not only is that the case in the instance of the 
action which I have mentioned here, but in a great 
number of other cases of considerable interest and im¬ 
portance,—bodies which act chemically with considerable 
energy when allowed to do so, are prevented by others 
from so doing when those others are trying to do the 
same thing. If, for example, we put metallic copper into 
nitric acid, the copper would dissolve with immense 
energy: it would undergo -what I might call a process of 
combustion. Again, if I put mercury in contact with the 
acid, the same thing would occur; it would be dissolved 
almost as rapidly as the copper. But if I put the two 
together into nitric acid, the copper prevents the mercury 
from undergoing combustion; and so far from en¬ 
couraging it to do the same thing, it actually takes from 
it the power which it possessed before of undergoing a 
combination of that kind. And more than that, if I take 
mercury which has been burned—a solution of mercury 
in the form of corrosive sublimate,—and put copper into 
it, the copper will actually unbum it, or make it come 
back again from the point at which it had got, and 
throw down the metal. You can see the process which 
takes place; on putting a strip of clean red copper into 
the solution, it becomes grey, and throws down the 
mercury from the solution. So far from encouraging 
the mercury to oxidation, it makes it do the opposite to 
that which it otherwise had a tendency to do. 
Again, I will take some of this solution of copper—it 
ought to be some of the very solution which is being 
made here, where copper is being dissolved at the 
expense of mercury—and if I put into it a piece of 
common iron, perfectly clean and white, it will very 
speedily combine; and I cannot express its functions in 
combining better than by saying that it will make 
copper uncombine, for the copper which was burnt is 
now being unburnt. 
If we go carefully, with the knowledge of their par¬ 
ticulars, through the best-known chemical processes, we 
find that there is, as a rule, a force at work which I 
might describe as polarity—a tendency among con¬ 
tiguous particles which are acting on one another to 
assume functions which can be best characterized as 
being opposite to one another. Whatever the one is 
doing, the other is doing as nearly as possible the very 
opposite of it, and any tendency to do like w r ork I know 
not of. There are, however, cases which -would appear 
to be favourable to the notion of contagious chemical 
action. If I blow out that gas-burner, still letting the 
gas escape, and then bring near to it a burning splint, it 
will set fire to the gas, and the same with a candle-wick if' 
I bring close to it a burning match—the match, which is 
burning, communicates to the wick the pi’oeess which it 
is undergoing,—but the explanation is this, it does so 
merely because of the high temperature which it has 
attained. If by any other process, such as concentrating 
the rays of a powerfully-heated surface by means of a 
lens, I raise the temperature of the gas to that point at 
which it is capable of combining with the oxygen of the 
air, it will do just as well. The accident that the high 
temperature is communicated by the biu-ning splint has 
nothing to do with the process. 
(To be continued.) 
Hypodermic Injection of Calomel for Syphi¬ 
litic Diseases of the Eye. —Professor Quaglino and 
Dr. Soresina give the details of a considerable number 
of cases where this plan of treatment has been successful 
in various ophthalmic diseases of syphilitic origin. The 
calomel was sometimes injected hypodermically into the 
temples, sometimes into the arm, great benefit being ob¬ 
tained in every instance.— The Practitioner. 
