CHAPTER XVI. 



FORMIC AND LACTIC ACIDS. 



THESE two acids have not yet been mentioned, for 

 although their presence in wine may be justly 

 suspected it has not yet been proved. 



I have not been able to detect formic acid in Port, 

 Madeira or Teneriffe wines by distillation, and when 

 nitrate of silver and a little ammonia were added to 

 the distillate no silver was reduced. !sTo brown colour 

 was produced by means of caustic potash, so we may 

 conclude that no aldehyde is present in it. 



"With respect to lactic acid, lactate of lead is so- 

 luble. Lactic acid must therefore be sought in the 

 liquid obtained by precipitating the wine with sugar 

 of lead, basic acetate of lead, and ammonia, and then 

 filtering. 



"When this liquid (obtained from red Bordeaux) 

 has been freed from lead by sulphuretted hydrogen, 

 filtered and evaporated, the residue is easily soluble in 

 alcohol. This deposit, in which there was a good deal 

 of sugar, was digested with carbonate of zinc upon a 

 water bath, and freed with alcohol from sugar and 



