17 



Paris municipal laboratory test.a 



Three preliminary tests are used, and wines are considered genuine 

 as to color if they respond to these tests. 



(1) Sticks of chalk are steeped in a 10 per cent solution of egg albumen and dried 

 first in the air and' then at 100 C. The wine is tested by allowing two drops to fall 

 on a surface of the chalk from which the excess of albumen has been removed by 

 scraping. Genuine wines give a gray color, and young and highly colored wines 

 may give a somewhat bluish tint, but there should be no trace of green, violet, or rose. 



(2) The wine is made alkaline by baryta water until it is of a greenish hue. It is 

 then shaken up with acetic ether or arnylic alcohol. If the wine is pure there is no 

 color in the upper layer, with or without the addition of acetic acid. On the other 

 hand, coal-tar colors of a basic nature color the solvent and give indications suggestive 

 of amido-benzene, fuchsin, safranin, etc. 



(3) Ten cc of wine are made alkaline until the wine becomes of a green color by 

 the addition of a 5 per cent caustic potash solution. To this are added 2 cc of a solution 

 of mercurous acetate. The whole, after shaking, is filtered. With pure wine the 

 filtrate is colorless, both before and after acidulating with hydrochloric acid, while 

 coal-tar colors of an acid nature tint the filtrate red or yellow. 



Dupre test. *> 



A jelly is made by dissolving 5 grains of gelatin in 100 cc of warm water and 

 pouring the solution into a square flat mold made of paper. From this cake cubes 

 about three-fourths inch square are cut with a sharp wet knife and are immersed in 

 the wine, taken out after the lapse of from twenty-four to forty-eight hours, washed 

 slightly, and sections cut, in order to see how far the coloring principles have pene- 

 trated. If the wine is pure, the color will be confined almost entirely to the edges of 

 the slice, or will not have penetrated beyond one-sixteenth to one-eighth of an inch. 

 Most other coloring matters rapidly permeate and color the jelly. 



(1 ) Colors penetrating slowly: 



Coloring matter of pure wine. 

 Coloring matter of rhatany root. 



(2) Colors penetrating rapidly: 



Rosanilin. Litmus. 



Cochineal. Red cabbage. 



Logwood. Beet root. 



Brazil wood. Wayside mallow. 



Indigo. Marsh mallow. 



b. EXAMINATION FOR COAL-TAR COLORS. 

 Mansfield's test, a 



Dilute 25 cc of red wine in two large test tubes to 100 cc with water. Add a few 

 drops of hydrochloric acid to one and a few drops of ammonia to the other and 10 cc of 

 amyl alcohol to both. Agitate without shaking, allow to settle and drain off alcohol 

 from both. 



(1) Alcohol from acid solution. The amyl alcohol is colored red. On addition of 

 ammonia (dilute) the color becomes green and passes into the water solution, chang- 



Report on processes in use at the municipal laboratory, by Doctor Muter, analyst, 

 1885. 



&Blyth, Foods, etc., 5th ed., 1903. 



cDr. M. Mansfield, Zts. Nahr. Genussm., 1897, 55. 



9251 No. 2505 3 



