SUGAR AND ACID IN GRAPES DURING RIPENING. 7 



evaporating dish and replaced with hot distilled water. This ex- 

 haustion was repeated five or six times and the solution collected in 

 the porcelain dish. When the extraction seemed complete, cold dis- 

 tilled water was added to the beaker. The pulp in the cloth was 

 then carefully worked and pressed with the fingers to extract the 

 remainder of the soluble constituents, which was added to the extract 

 already collected. To determine whether the exhaustion was com- 

 plete the pomace in the cloth was again treated with boiling water 

 and a 10 cc portion titrated with tenth-normal sodium hydroxid, 

 using phenolphthalein as indicator. If not more than 0.5 cc of 

 tenth-normal sodium hydroxid were required to neutralize the por- 

 tion taken, exhaustion was considered complete. If the material 

 still showed appreciable acid the extraction with water was con- 

 tinued until complete. 



The solution collected from the successive boilings, after being 

 kept on a water bath until the volume was sufficiently reduced, was 

 transferred to a 500 cc graduated flask. The porcelain dish was care- 

 fully rubbed with a policeman and rinsed with hot water until all the 

 extractive matter was recovered. The solution was cooled to room 

 temperature and made up to 500 cc, and from this sample all the 

 organic determinations were made. The fruit samples were treated 

 in duplicate by this method and the results checked satisfactorily. 

 The average result of these two determinations, in percentage of the 

 weighed fruit sample, is given in Table 6. 



In order to determine more accurately the inorganic constituents, 

 such as phosphoric acid, chlorin, potassium oxid, sodium oxid, cal- 

 cium oxid, and magnesium oxid, weighed portions of the same fruit 

 sample were ashed direct for these determinations. An attempt was 

 made to use the solution extract for the determination of chlorin, 

 but it was found by check determinations that this solution gave a 

 large excess of chlorin, indicating that chlorin was probably intro- 

 duced in some manner during the preparation of the solution. The 

 fruit for these determinations was ashed in platinum dishes in the 

 usual manner, 50 to 80 gram samples being used. The results are 

 given in percentage of the weighed sample. 



METHODS OF ANALYSIS. 



The official methods for wine (Bureau of Chemistry Bulletin 107, 

 Revised) were followed in the work done during 1911, save for cream 

 of tartar, free tartaric acid, tartaric acid to alkaline earths, and for 

 the item reported as fixed acid other than tartaric. For determin- 

 ing these substances, except the last named, the revised methods 

 given (Bureau of Chemistry Bulletin 162, pages 71 to 77) were fol- 

 lowed, and in the results reported for 1912 the total tartaric acid 

 was determined by the revised method given in this bulletin. These 



