APPENDIX B. 385 



allowed to stand twelve hours. The shaking and standing of the solution must take 

 place at as nearly as possible the satue temperature. If any considerable precipitate 

 forms during this time free tartaric acid is present, and the estimation of it and of 

 the bitartrate of potash may be necessary. 



(b) Quantitative estimation of the bifcartrate of potash and free tartaric acid: la 

 two stoppered flasks two samples of 20cc. of wine each are treated with 200cc. ether- 

 alcohol (equal volumes), after adding to the one flask 2-3 drops of a 20 per cent, solu- 

 tion of acetate of potash. The mixtures are well shaken, and allowed to stand 16-18 

 hours at alow temperature (0 10 C.), the precipitate filtered off, washed with ether- 

 alcohol, and titrated. (The solution of acetate of potash must be neutral or acid. The 

 addition of too much acetate may cause the retention of some bitartrate in solution. ) 

 It is best on the score of safety to add to the filtrate from the estimatiou of the total 

 tartaric acid a further portion of 2 drops of acetate of potash to see if a further pre- 

 cipitation takes place. 



In special cases the following procedure of Nessler and Barth may be used as a con- 

 trol : 



Fifty cubic centimeters of wine are evaporated to the consistency of a thin sirup 

 (best with the addition of quartz sand), the residue brought into a flask by means of 

 small washings of 93 per cent, alcohol, and with continual shaking more alcohol is 

 gradually added, until the entire quantity of alcohol is about lOOcc. The flask and 

 contents are corked and allowed to stand four hours iu a cool place, theu filtered, and 

 the precipitate washed with 915 per cent, alcohol; the filter paper, together with the 

 partly flocculeut, partly crystalline, precipitate, is returned to the flask, treated with 

 39cc. warm water, titrated after cooling, and the acidity reckoned as bitartrate. The 

 result is sometimes too high if pectiuous bodies separate out iu small lumps, inclosing 

 a small portion of free acids. 



In the alcoholic filtrate the alcohol is evaporated, 0.5cc. of a 20 per cent, potassic 

 acetate solution added, which has been acidified by a slight excess of acetic acid, and 

 thus the formation of bitartrate from the free tartaric acid in the wine facilitated. 

 The whole is now, like the first residue of evaporation, treated with (sand and) 96 

 per cent, alcohol, and carefully brought into a flask, the volume of alcohol increased 

 to lOOcc., well shaken, corked, allowed to stand in a cold place four hours, filtered, 

 the precipitate washed, dissolved in warm water, titrated, and for one equivalent of 

 alkali two equivalents of tartaric acid are reckoned. 



This method for the estimation of the free tartaric acid has the advantage over the 

 former of being free from all errors of estimation by difference. The presence of con- 

 siderable quantities of sulphate* impairs the accuracy of the method. 



Mulic acid, siiccinic acid, citric acid. Methods for the separation and estimation of 

 these acids cannot be recommenced at the present time. 



Salicylic acid. For the detection of this,100cc. of wine are repeatedly shaken out with 

 chloroform, the latter evaporated and the aqueous solution of the residue tested with 

 very dilute solution of ferric chloride. For the approximately quantitative determi- 

 nation it is sufficient to weigh the chloroform residue, after it Uas been again recrys- 

 talli/ed from chloroform. 



Coloring matter. Red wines are always to be tested for coal tar colors. Conclusions 

 iu regard to the presence of other foreign coloring matters drawn from the color of pre- 

 cipitates and other color reactions are only exceptionally to be regarded as safe. In 

 the search for coal tar colors the shaking out of lOOcc. of the wine with ether be- 

 fore and after its neutralization with ammonia is recommended. The etherial solutions 

 are to be tested separately. 



Tannin. In case a quantitative determination of tannin (or tannin and coloring 

 matter) appears necessary the permanganate method of Neubauer is to be employed. 

 As a rule the following estimation of the amount of tannin will suffice: The free 

 acids are neutralized to within 0.5 grams iu lOOcc. with standard alkali, if necessary. 

 Then Ice. of 40 per cent, sodic acetate solution is added, and drop by drop a 10 per 

 cent, solution of ferric chloride, avoiding an excess. One drop of ferric chloride is 



