§ 142. WINE. 281 



ference between the amounts of sodic solution required in 

 the two trials represents the acetic acid. 



Estimate 0.06 grm. of acetic acid, HC^HgO^, for every 

 cubic centimetre of this difference, and 0.075 grm. of tar- 

 taric acid, H^C^H^Og, for every cubic centimetre of the 

 sodic solution required after the acetic acid was expelled. 



Griffin {Chemical Testhig of Wines and Spirits) deter- 

 mined the free acid as follows, with a ^ 1^^ atomic solution 

 of ammonia for the standard solution, and an extract of 

 logwood for the coloring matter. 



Take two portions of wine, of "7.5 c.c. each, and add to 

 each, if it is a white wine, 125 c.c. of water, or, if it is a 

 red wine, 250 c.c, or more, according to the depth of the 

 color ; then add exactly the same quantity of the e:?;tract 

 of log^yood to each portion, which gives a color to the 

 wine very much like that obtained by painting j^aper 

 with raw sienna; add the alkaline solution from the 

 burette to one portion, keeping the other at hand for 

 comparison, with constant stirring ; when the color sud- 

 denly changes to a reddish-brown, like that obtained by 

 hurnt sienna on paper, the point of saturation is reached. 

 Now, repeat the experiment with the other portion of the 

 wine, adding all but 2-3 c.c. of the required quantity of 

 standard ammonic solution at once, and then drop by 

 drop, until the acid is saturated. 



Each cubic centimetre of the alkaline solution required 

 corresponds to 0.1 of an equivalent of free acid, or, if we 

 call it all tartaric acid, as it is, mostly, 0.0075 grm ; and 

 in this case the number of cubic centimetres used gives 

 at once the number of grammes of acid (tartaric) in the 

 litre of wine. 



Good wines contain 4—6 grms. of free acid in the litre 

 (300-400 grains of crystallized tartaric acid, Griffin). In 

 poor wine years, the proportion of free acid often rises 

 as high as 10-12 grms. in the litre. 



I Tartar.— Add 40 c.c. of 90°L alcohol to 20 c.c. of 



