METHODS OF ANALYSIS. 



15 



COLOR DETERMINATION. 



The method for color determination was that used by this labora- 

 tory in cane sirup work. The standard colors were prepared accord- 

 ing to the following method : 



The materials used are (1) pure glycerin and (2) a caramel solution, which is prepared 

 as follows: 



Heat 6 grams of pure sugar to 212 C. for one-half hour in a flat-bottomed aluminum 

 dish and dissolve the caramel formed in boiling water, evaporate to a small volume, and 

 make up to 200 cc with glycerin. The oven for caramelizing the sugar (fig. 1) is con- 

 structed as follows: 



A and A 7 are heavy sheets of asbestos board 18 cm (7 inches) square, A' being per- 

 forated near one edge by a hole for the cork supporting the thermometer d; 6 is a sheet- 

 iron cylinder 15 cm (6 inches) in diameter; c is a tin 

 can 9 cm (3 inches) in diameter, which is filled with 

 paraffin to within 1 cm ($ inch) of the top. This can 

 rests on the pipestem triangle e. The bath or oven 

 is supported on a tripod and is heated by two burners. 

 One burner is so adjusted as to keep the bath at 

 512 C. 



Bring the temperature of the oven up to 212 C., 

 using both burners. Then remove the asbestos cover 

 carrying the thermometer and place 6 grams of sugar 

 in a flat-bottomed aluminum dish 7 cm (2| inches) in 

 diameter and 1.5 cm (f inch) deep, and put it in the 

 can containing paraffin. Replace the cover at once 

 and as soon as the temperature reaches 208 C. turn 

 out one burner and keep the bath at 212 C. by 

 carefully adjusting the other one. At the expiration 

 of thirty minutes from the time the sugar was placed 

 in the bath, dissolve in boiling water, and make up 

 as described. The aluminum dish should not be less 

 than 1 .5 cm (| inch) deep, since the sugar melts before 

 caramelizing and runs to one side of the dish, which, 

 if too shallow, will tilt, fill with paraffin, and sink. 



With the ingredients thus prepared, the scale of colors is made up by mixing as indi- 

 cated in the following table: 



Amounts of ingredients to be used in preparing solutions for the color scale. 



FIG. 1. Apparatus for preparation 

 of standard caramel. 



The standard colors were placed in 1-ounce screw-capped vials of perfectly clear 

 glass, having the same internal diameter. The sample to be examined was placed in a 

 vial of the same size and the colors compared by transmitted light. 



