18 



Color reactions using different solvents under varying conditions (Frost). 

 GROUP A. 



GROUP B. 



Color of filtrate... 



GROUP C. 



A piece of fat-free white wool cloth, 10 cm square, was boiled five to ten minutes 

 in 50 cc of wine to which were added 50 cc water and a few cubic centimeters of 

 dilute hydrochloric acid. The cloth was removed and washed in a stream of water. 

 The dyed cloth matched OR-T2; treated with strong ammonium hydroxid, it became 

 yellow-green, matching Y-BTM. 







THE DETERMINATION OF TOTAL, FIXED, AND VOLATILE ACIDS IN WINES. 



The first methods of determining the volatile acids in wines consisted in distilling 

 a measured quantity of the sample to about one-third of its original volume and 

 titrating the distillate; the results must obviously have been too low. The next step 

 appears to have been in favor of an indirect course of procedure whereby the total 

 acids were first titrated, then another portion of the wine evaporated off and the fixed 

 acids titrated in the residue. From the difference between these titrations was 

 calculated the amount of volatile acids. Various modifications of this method came 

 into use, in all of which the aim appears, to have been to liberate the total volatile 

 acids by a prolonged heating of the extract. That an appreciable change might 

 occur in the extract constituents as a result of such treatment was not at first conceived. 

 At a later date, however, there developed grounds for the belief that certain of the 

 fixed acids disappeared, in consequence of which on titrating the residue there was 

 obtained too small a result; hence the result for volatile acids would be too high. 

 These considerations finally resulted in the abandonment of the so-called indirect 

 methods, and it was again proposed to separate the volatile from the fixed acids by 

 means of distillation and to titrate the volatile acids in the distillate.^ But because 

 the volatile acids pass over only slowly and with difficulty, a simple distillation, as in 

 the determination of alcohol, could obviously not be employed. Following a number 

 of attempts which had been made to devise a successful method, Lindemann,& in 



a Methods proposed by Kissel, Weigert, Nessler and Barth, and Wolff: Zts. anal. 

 Chem., 1869, 8: 416; 1879, 18: 208; 1883, 22: 166; Repert. anal. Chem., 1883, 1: 213. 

 b Zts. anal. Chem., 1883, 22: 516. 



