23 



in carrying "ut the titrations, and the results were scarcely better when litmus tine- 

 tun- was ued. In titrating according to the Windisch methods the point of neu- 

 trality was judired to be attained when a small drop of the liquor placed on delicate 

 bin.- litmus paper just ceased to produce a perceptible red. There appeared to 

 In- decided disadvantages in using litmus paper, and the use of litmus tincture even 

 in a dear distillate t~ open to serious objections, which will be stated presently. 

 In colored wines e-pe< -ially the difficulties were very great, and it was found well- 

 ni;h impossible at times to devise a means whereby to judge with reasonable cer- 

 tainty the true end-point of the titration. It was found, however, after considerable 

 practice, that fairly -onconlant results were obtainable by this method in the ma- 

 jority Hi instances Phenolphthalein, on the other hand, while not entirely unob- 

 jectionable, was found to give far greater satisfaction. While it was not always 

 convenient to titrate on the undiluted sample, especially in the case of wines con- 

 taining more ,,r Ian natural coloring matter, it was found to be entirely permissible, 

 'he titration .,f rider \ in. -ar-. to dilute with boiled distilled water in order to 

 carry out a .-ucce-.-fiil titration with phcnolphthalein. It has been shown that the 

 Mid-point of a titration can he very accurately judged, even in a deeply-colored 

 win.-, ami that the addition of water to the extent of 100 or 200 cc does not introduce 

 tana error in the result. A- in a cider vinegar, the change in the color of a wine 

 occurs at a much earlier stage than the change in the indicator and there is never a 

 H difficulty in -af.-ly judging the end point. 



As already pointed out. the results shown in the first column of figures are at best 

 only rough approximation-. In the majority of instances it was observed that when 

 litmus paper wa- u-.-d the til rat ions were carried somewhat beyond the point of 

 neutrality which -cemed to he indicated by the change in the natural coloring matter 

 of the wine. It i^ al-o noted that the results obtained by the titmtions employing 

 litmus were uniformly much lower than the result* obtained with phenolphthalein. 

 Thi- is inii- n-.i only in the titration- of total and fixed acids, but also in the direct 

 titration- of the volatile acid-. **n the basis of the results obtained with phenolph- 

 thal.-in. litinii- indicates approximately fn.m 77 to 92 per cent of the total acids and 

 from 58 to 85 per cent of the fixed acid-. Doubtless there are theoretical reasons 

 underlyinu' the-e ,! and the question may well be raised as to whether 



cheii:: -iviMi due attention to these considerations in choosing indicators for 



titrating the arid- in wines. 



In the tir-t place, there appears to be little justification for the practice adopted 

 by some chemi-t- of employing the natural coloring matter as a correct indicator in 

 titratinu' either the total or fixed acid-. Little of value is known regarding the action 

 of the oenocyanin or other coloring -ub-tances in the presence of acids or alkalies, 

 and it is certain that -u< -h .-ub.-tam -e- have not been recommended in the titration 

 of any of the common acids. In the rase of litmus also there are some important 

 considerations which should bar it as an indicator for wines as well as fruit products 

 in general. Litmus i- not recommended for titrating such acids as tartaric, acetic, 

 tannic, succinic, or malic. In titrating tartaric acid with this indicator, the change 

 is gradual and the end-point indistinct, while in titrating acetic acid, the acetate 

 of sodium formed i- alkaline to litmus and tends strongly to hasten the end-point. 

 On titrating solutions of tannic acid, a change takes place almost immediately on 

 beginning the titration, and only a small proportion of the actual acid is indicated. 

 Phenolphthalein, on the other hand, is a very satisfactory indicator with all these 

 acids, and, with the exception of tannic acid, the theoretical amount of acid is obtained. 

 About 80 per cent of tannic acid is indicated, but the total acid is obtained after 

 boiling with a measured small amount of tenth-normal hydrochloric acid. 



