September 3, 1870.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
195 
with it. There are many other processes by which we 
could get it, but the actual process by which we do get 
it is a process in which this vital organism, the vinegar- 
plant, is the agent of its formation. It might be made 
by mere processes of combustion, but it is made by a 
process of fermentation. 
There is one singular feature in the first and best 
known of these processes—the alcoholic fermentation— 
which you will notice when I tell you something of the 
way in which the processes of fermentation present them¬ 
selves, even without very great care on the part of the 
observer. If, for instance, you were to express the juice 
of some sweet fruit—say grapes—and if you were to 
leave that expressed juice in contact with the air for a 
little time, having first squeezed it through some suitable 
cloth or filter, so as to have it clear, of course there 
would be no solid particles in it when you put it aside; 
but, if you leave that in a tolerably warm place, in con¬ 
tact with the air, you would find that little solid particles 
would appear in this juice, that they increase in number, 
and that, in proportion as they increase in number, and 
as the quantity of them becomes greater, so does the 
process of effervescence—the evolution of gas from the 
grape juice—become more and more rapid. These little 
solid particles, which are not present at first in the grape 
juice, but which gradually make their appearance when 
it is exposed to the air, are what we commonly call, 
in the ordinary case of alcoholic fermentation, in this 
country, yeast—either beer-yeast or wine-yeast; it is 
the same organism in each case. The peculiarity of the 
process is this, that these substances—this yeast—which 
seems to make the sugar into those products which 
I enumerated to you, does not disappear while doing 
the work, but is produced by the very process. The 
more active the production of these yeast-cells, and 
the more speedy the growth of these yeast-cells, the 
more effective and rapid is the process of fermentation, 
and no fermentation of the kind which I am speaking of 
at present—the alcoholic fermentation—has ever been 
known to take place in the absence of these organisms. 
That circumstance I just mention briefly at present, but 
the fact that these yeast-cells appear whenever the 
process is going on—and the more they grow the more 
rapid is the fermentation—has led people to suppose at 
first, and to believe afterwards, that these yeast-cells 
were the agents of the transformation, the active sub¬ 
stances which decomposed the sugar in contact with the 
water, and induced the transformation which we noticed. 
Now, the very fact that one of the two substances which 
are reacting upon one another chemically (because the 
changes are chemical in their fundamental nature), 
should not disappear, but should rather increase by the 
process, is entirely anomalous—it is entirely at variance 
with the simplest and best known facts of chemistry, so 
much so, that if it were not established upon incontro¬ 
vertible evidence, I believe that most chemists would be 
inclined to disbelieve it, and to say it cannot be,—it is 
impossible,—it is a mistake. If you tell me, as a chemist, 
that this yeast is transforming sugar by its action on the 
sugar, and that instead of being consumed the yeast is 
actually increased in quantity by doing that work, I 
should say it is nonsense—it cannot be, because in all the 
cases of chemical action which I know best, nothing of 
the kind occurs, but the very opposite. When one sub¬ 
stance acts upon another, each one disappears in the 
process, and is transformed into a product having other 
properties. I need hardly give you illustrations of that; 
but one or two simple cases may not be useless, as serv¬ 
ing to fix clearly this important circumstance in your 
minds. 
I will take at first one of a particularly elementary 
and simple kind,—a process of combustion. I will take 
a little strip of metal—magnesium wire—and will hold 
it for a short time in the flame of a spirit lamp, so as to 
raise it to a sufficiently high temperature. The light 
you see emitted is due to the combustion of the oxygen 
in the air with the metal magnesium, w r hich I hold in 
my hand. This is one of the simplest possible cases of 
chemical action. The metal has disappeared. The strip 
of wire is gone, and oxygen from the air disappeared 
also. At the same time a white powder was formed. I 
dare say you did not notice it, but here is a quantity of 
the same substance in a bottle. It consists of oxygen 
from the air combined with the metal magnesium, and 
the point is this—that all the magnesium which took 
part in that process disappeared and went to form this 
white powder, and all the oxygen which took part in the 
process also disappeared. The two united together, each 
disappeared as such and went to form this new product. 
And, moreover, we.can tell, from an examination of the 
proportions in which the substances combine, exactly 
what weight of oxygen would disappear for every part 
by weight of magnesium. If you burn, for instance, 
three grammes or three pounds of magnesium, you 
would require exactly two grammes or two pounds of 
oxygen. For instance, three pounds weight of magne¬ 
sium would combine with two pounds weight of oxygen, 
and the product of the two together would be five 
pounds in weight. I may show you the same thing 
with soda, not the substance which is commonly called 
by that name, which is a carbonate of that base. I have 
here a little pure soda solution in a bottle. I will pour 
some into a beaker-glass, and I will show you one pro¬ 
perty which characterizes it, viz. that of changing the 
colour of this red paper into blue. Now, I will pour 
some of this acid body, the oil of vitriol, into another 
beaker-glass. If I put the paper which has been dis¬ 
coloured into this pure acid, it would be dissolved; but 
I will dilute some of it with water, and then you will see 
that paper, which has been rendered blue by the agency 
I have just used, is brought back again to red by the 
agency of this acid. Now, if I mix the acid with the 
soda, we shall have audible evidence of violent action 
going on. I will not go on with the process, but I have 
purposely taken the two substances in presence of very 
little water, in order to show you that the heat evolved 
makes the liquid boil with great violence. I could have 
avoided that by adding water in the first place, but I 
wished to show you the vigour with which they unite 
together. If I were to go on adding acid to the soda, 
little by little, feeling my way until I had just completed 
the action, I should have got some water formed and 
some of the beautiful salt which I have here,—a body 
which is neither soda nor acid; it is a salt called Glauber 
salt or sodic sulphate, and all my materials would have 
disappeared in the process. If I use them in proper 
proportions, all the acid and soda would disappear and 
go to form these two other products. I might dissolve 
some of this sulphate in water, and might put red paper 
or blue into it and it would not affect either of them-; it 
is perfectly neutral in that respect. The proportion by 
weight in which this combination takes place is this. If 
I add 40 parts by weight of soda, and 49 of oil of vitriol 
in a state of purity, I should have as the result, 18 parts 
by weight of water, and 71 of sodic sulphate, and if I 
add together the weight of my materials and the weight 
of my products, I get the same—89. Nothing disappears 
in the process; all the acid and all the base which takes 
part in it is employed. Each particle which took part 
in the process disappeared as such, and it passed over 
into another form. 
I will mention one other case, because it is somewhat 
more complex. I may take the case which I was show¬ 
ing you just now, the white marble and hydric chloride 
or muriatic acid, which I used for making the carbonic 
acid gas. In that case, I used two materials, carbonate of 
lime, as it is commonly called, and hydrochloric acid. 
We get three products; on the one hand is a salt, 
which is commonly called chloride of calcium, a solid sub¬ 
stance used for drying gases, as it has a great affinity for 
water; another is water; and the third, as I showed you, 
carbonic acid gas. There, again, we have precisely the 
