16 



Comparison of methods for the determination of reducing sugars in wines. 



EXAMINATION OF THE NATURAL COLORING MATTER IN WINE. 



The following statement was contributed by Genevieve Imus, St. Paul. Minn. A 

 complete tabulation of results of tests made on wine colors is given in the Twelfth 

 Biennial Report of the Minnesota State Dairy and Food Department, pages 250 to 253. 



During the past two years a considerable amount of time has been given to the 

 examination of the natural coloring matter of wine. The work has not included the 

 detection of coal-tar dyes or other added colors but was intended primarily for the 

 purpose of obtaining on samples of known purity data that would be of value as criteria 

 in future routine analyses. The plan of making all color comparisons and descriptions 

 with reference to reliable standards has been adopted, and to this purpose the color 

 standards employed by Mulliken in his book entitled "A Method for the Identifica- 

 tion of Pure Organic Compounds," have been found to be admirably suited. These 

 standards consist of 18 pure colors, and of derived tones, 36 tints, 36 shades, and 12 

 medium broken colors. They are mounted on cardboard in compact form to facilitate 

 their use in the laboratory. A description of the standards and a discussion of the 

 application of color reactions to the examination of unknown substances are given by 

 Mulliken on pages 230 to 234. In matching colors the best results are obtained if 

 the operator stands with his back to a window and not in direct sunlight: The mate- 

 rial to be examined should be held about an inch away from the white cardboard 

 accompanying the color charts and alongside the square opening. The cardboard is 

 moved about until the exposed color matches as nearly as possible the color of the 

 material. A clear day is necessary for satisfactory results. 



The tests which are described below were made upon the undiluted wine unless 

 otherwise stated. In tests with the various reagents the resulting colors of the solu- 

 tion have been noted as well as the color of any precipitate which may have been 

 formed. In the solubility tests with amyl alcohol the colors of both the alcohol and 

 resulting wine have been matched on the color chart. and recorded. 



(a) About 5 ccof the sample are poured into each of six test tubes and the folio wing 

 solubility tests are applied: To each of two portions, one acidified with a few drops 

 of hydrochloric acid and one made alkaline with ammonia, 5 cc of ether are added. 

 To each of two portions, made, respectively, acid and alkaline in the same manner, 



