slowly. I therefore think it would be scarcely possible to 
ascertain the length of time that the wine had been in bottles, 
and am inclined to believe that the amount of change observed 
on adding sulphite of soda corresponds more closely with the 
time that the wine had been previously kept in the cask. I 
have especially observed this in the case of Bordeaux and Bur- 
gundy wines. Those of this type which I have hitherto 
examined seem to contain a larger relative amount of the B 
colour, when a few years old, than ordinary ports, and in this 
respect agree with the so-called natural port ; but the rate of 
change is greater when they are kept for some years, probably 
owing to their containing a less amount of alcohol. There is 
also a greater variation in different samples of the same age 
than I have met with in port wine, which is probably 
because the amount of alcohol in such wines varies more in 
proportion to the total quantity. 
It appears, therefore, that the natural colour of dark grapes 
is changed by oxidization into the somewhat similar colour 
found in new wines, and that by still further oxidization this 
is converted into another entirely different colour, which 
becomes much paler by further oxidization. The rate at 
which these changes take place varies according to circum- 
stances, but, other things being equal, it varies according to 
the time of the action. Much also depends on the deposition 
of colour in the form of crust, and after a long time the original 
dark coloured substance is almost entirely lost, and only an 
amber colour remains in solution, which behaves with reagents 
precisely like that in sherry wines. 
On White Wines. 
The colouring matter of white wines appears to be derived 
from one of those yellow substances, soluble in water, of 
which there are several of materially different character in 
the faded leaves of different kinds of plants, as more fully 
described below when treating on hops. That met with in 
the orange-coloured leaves of the beech is a good example. 
The depth of the colour is made nearly ten times as great by 
the addition of ammonia, and when dissolved in strong sul- 
phuric acid diluted with an equal bulk of water, oxidizing 
reagents first turn it much darker, and then much paler. 
When, however, kept for some months dissolved in dilute 
alcohol it turns to a much darker tint, and then the solution, 
with excess of ammonia, is only twice as dark as when made 
acid by citric acid. Oxidizing reagents added to the solution 
in sulphuric acid do not make the tint any deeper, and thus 
it appears as if it had been changed by oxidization into an 
