14 



distillation Titrate the 50 cc distillate with one-tenth normal sodium hydroxid, 

 u.-ing phenolphthalein as an indicator 



Stop the distillation when an additional 10 cc of distillate requires only one drop 

 of the standard alkali solution to neutralize. Usually 80 cc of distillate will include 

 practically all of the volatile acids. . . 



On cooling the apparatus the liquid remaining in the inner flask is siphoned into 

 the outer flask Rinse out the remaining small amount of sample by running several 

 portions of hot -water through the funnel tube and Disconnect the two flasks. In 

 case of a light colored wine or a white wine, add 100 to 200 cc of recently boiled dis- 

 tilled water and titrate with one-tenth normal sodium hydroxid, using phenol- 

 phthalein as an indicator. In the case of a highly colored wine, after cooling the liquid 

 make up to 100 cc, measure out 25 cc, dilute with recently boiled distilled water and 

 titrate as before. Express the results for ,-olatile and fixed acids as cubic centi- 

 meters of normal acid in 100 cc of the wine. 



THE DETERMINATION OF GLYCEROL IN WINES. 



The method submitted to collaborators has been subjected to trial on a dozen 

 samples of genuine California wines. After the residues obtained by the method 

 had been weighed, they were analyzed for glycerol by the acid-dichromate oxidation 

 method, as follows: 



The residue was dissolved in a little distilled water, filtered and washed through 

 a previously dried and weighed small filter, and the solution made up with water 

 to 50 or 100 cc, the volume depending on the amount of the dissolved residue. An 

 aliquot portion of the solution (equivalent to from 0.3 to 0.5 gram of residue) was 

 run into a 200 cc beaker, 20 cc of sulphuric acid (1:1) and 50 cc of standard potassium 

 dichromate solution (1 cc equivalent to 0.01 gram of glycerol) run in and the beaker 

 placed in boiling water. During the heating the strength of a prepared solution of 

 ferrous-ammonium sulphate (240 grams in 1,000 cc) was determined by titration with 

 the dichromate. At trie end of two hours the beaker was removed from the boiling 

 water, 100 cc of water added, and the excess of dichromate titrated with the ferrous- 

 ammonium sulphate. From the result of the titration the weight of the oxidized 

 glycerol was calculated. 



A sample of chemically pure glycerol, which by specific gravity determination and 

 refractometer reading was shown to be 99.3 per cent pure, gave by this method 97.7 

 per cent pure glycerol by weight. The filter containing the residue insoluble in 

 water was again dried at 100 C., cooled in a desiccator and weighed. Tannin was 

 determined in another aliquot portion of the solution by the official provisional 

 method given for tannin in wine. The results of these determinations are shown in 

 the accompanying table. In three instances, owing to insufficient material, no results 

 for tannin were obtained. 



There seem to be no means of estimating the loss of glycerol which takes place 

 during the determination. It appears, however, that the material which is extracted 

 and weighed as glycerol is never pure glycerol, as is generally assumed. The pro- 

 portion of glycerol obtained by the method of oxidation ranges from 84.7 to 88.5 per 

 cent of the weighed residues. Also it appears that in some cases a considerable 

 amount of the residue consists of matter insoluble in water, and also tannin. 



Mr. C. S. Ash, chemist of the California Wine Association, recognizes the need of 

 an improved method for the determination of glycerol, and describes the following, 

 which has been employed in his laboratory: 



Measure put 100 cc of wine in a porcelain dish, evaporate to a thick sirup, then 

 make alkaline with milk of lime and evaporate almost to dryness. Dissolve out the 



flycerol with successive portions of boiling hot alcohol, evaporate the alcohol to about 

 cc, transfer to a stoppered flask or cylinder of 100 cc capacity, make up to 100 cc with 

 acetic ether, and allow to stand over night. Filter the liquid from the precipitate, 

 evaporate off, and dry the glycerol to constant weight at a temperature not above 55 

 or 60 C. 



The method is said to give fairly uniform results, and the most unsatisfactory part 

 of the procedure is the evaporation of the solvent. A small percentage of glycerol is 

 undoubtedly lost, especially toward the end of the process, but this and other diffi- 

 culties, it is hoped, may be overcome in great measure. 



