266 INTERNATIONAL CONGRESS OF VITICULTURE 



used. One evaporation and two evaporations were carried out and the loss 

 in acid determined. Where no NaCL was used, there was a tendency for 

 the extract to darken and make titration difficult; where NaCL was used 

 no such difficulty was met. 



Cms. of NaCL Volatile Volatile 



Volatile used in NaCL Acid by Acid by 



Acid by Method for One Two 



Distillation 20 c. c. Wine Evaporation Evaporations 



.089 .048 .087 



.089 2 .073 .090 



.089 5 .048 .072 



In general, the agreement between the two methods was satisfactory. 



Better agreement was found with samples containing small amounts of 



volatile acid than large amounts. 



Effect of NaCL Concentration. 



To 20 c. c. samples of decolorized wine were added 1, 2, 5, 10 gms. 

 NaCl respectively and the solutions evaporated twice till NaCl separated. 

 The samples were diluted and titrated. 1 and 2 grams gave about the same 

 results. 5 and 10 grams gave too low results. This is because the large 

 amounts of NaCl super-saturate the liquid more quickly as the wine is concen- 

 trated and give too short a time for the expulsion of the volatile acid. The 

 smaller amounts increase in concentration more gradually as the volume 

 decreases during boiling. The boiling point is increased and this increased 

 boiling point drives out the acetic acid more effectively than is possible with 

 wine to which no NaCl is added. 



The NaCl serves as an indicator for the point at which to stop boiling 

 and is useful in this way. 



It also checks charring of the sample caused by evaporating too far; 

 the protective action in this respect is very marked. 



The figures show that two evaporations are necessary with 2 gms. NaCL 

 and that two evaporations with 5 gms. NaCL gives low results. 



The method and apparatus needed are simple as the following list of 

 reagents and apparatus necessary and outline of method will indicate: 



Apparatus: (1) Gas or alcohol burner; (2) wire gauze for burner; (3) 

 several 200 c. c. Erlenmeyer flasks; (4) two 20 c. c. pipettes; (5) glass funnel, 

 3-inch; (6) filter paper for funnel; (7) 50 c.c. burette graduated to 1/10 c. c.; 

 (8) burette stand. 



Reagents: (1) N/10 alkali; (2) phenolphthalein indicator solution; (3) 

 pure bone black as free from mineral salts as it can be made or pure vege- 

 table charcoal free from mineral salts. 

 Summary of Methods: 



1. Decolorize about 75 c. c. of the sample with bone black or vegetable 

 charcoal free from carbonates. Filter. 



2. Titrate 20 c. c. with N/10 alkali; record c. c. "a"; the titration is 

 made directly in the flask itself; no breaker is necessary. 



3. To 20 c. c. add approximately 2 gms. NaCL. Evaporate 200 c. c. 

 Erlenmeyer till NaCL separates and liquid spatters slightly. 



4. Add 20 c. c. distilled water and evaporate again till NaCL separates. 



5. Add distilled water and titrate. Record c. c. as "b". 



6. (a-b) X .03 %volatile acid. 



