736 Agricultural Journal of Victoria. 



a sliglit cloud appears whicli eventually becomes a flaky precipitate 

 which falls to the bottom of the vessel leaving the liquid hardly 

 at all coloured, and perfectly transparent. Under the same con- 

 ditions the liquid containing tannin without albuminous matter 

 colours but with no precipitation, and we know that this colouration 

 of tannin in an alkaline solution is due to the oxidation which takes 

 place in the above experiment in favour of the oxygen contained in 

 the liquid in solution. On the other hand, the same solution con- 

 taiuino- albumen without tannin does not precipitate when rendered 

 alkaline. It is, therefore, the combination of both tannin and albumen 

 that was oxidised just now. Besides if, before alkalization, this- 

 liquid is boiled so as to get rid of all the oxygen dissolved in it, and 

 it is kept from contact with the air after alkalization it only colours 

 slightly and remains almost limpid. But as soon as the liquid is 

 strongly aerated the cloud appears at once, and the colour deepens. 

 In this experiment the oxidation which has brought about the coagu- 

 lation of the combination of tannin and albumen has been purely 

 chemical. In the case of wine, the medium is always acid. Oxidation 

 of the oenotannin is produced however, although more slowly as in 

 the following conditions : — 



A young white wine is bottled without much care, preferably 

 with tapered corks which do not touch the liquid, and the bottles are 

 left standing for some weeks. In certain of these samples the free 

 surface of the wine, in contact with the air enclosed in the neck of the 

 bottle, will be invaded with Mycoderma mni or aceti, the activity of 

 which will be sustained by the easy diffusion of the air contained in. 

 the bottle, and the outside atmosphere. No account must be taken 

 of these samples. Only those that happen to have been deprived of 

 any germs of disease will be used to observe the phenomena of 

 clarification. After a certain time the opalescence increases, the wine 

 becomes very cloudy, and then a fine precipitation is formed some- 

 times flaky, and is deposited little by little on the bottom of the 

 bottle, with a pronounced brown colour, while the rest of the wine 

 remains absolutely limpid. The precipitation can then be easily 

 separated, either by decantation or filtration. At this moment other 

 changes are noticeable in the wine, the colour is more yellow, and the 

 wine tastes flat. The wine is slightly " casse " (broken) which,, 

 while being favorable to clarification and consequently to a certain 

 amelioration, has passed the desired aim, and has consequently toa 

 much affected the colour and taste. These modifications are naturally 

 of a greater or less intensity according to the quantity of oxidase the 

 wine contains. It is known that wines from perfectly healthy grapes 

 only contain traces brought by the pulp of the grape, while if the grapes 

 are rotten the quantity of oxidase will be increased. 



If this influence of the air is to be made use of it must be 

 with care, hence frequent racking into slightly sulphured casks. 

 Sulphurous acid, without completely preventing the action of oxidation 

 and coagulation above referred to, is the most handy and eflicacious 

 corrective ao-ainst over oxidation of a wine. 



