186-188] Details of Juice Analysis ny 



twenty minutes. Filter into a ioo-c.c. flask, and wash the 

 precipitate well with successive small quantities of hot water 

 until the filtrate measures rather less than ioo c.c. ; neutralise 

 with KHO. Cool the flask, and make up to ioo c.c. Trans- 

 fer to a burette, and determine the glucose with Fehling's 

 solution (paragraphs 82-84). 



186. Total Solids. — Evaporate the 50 c.c. measured into 

 the dish until a scum forms on the surface. Weigh a piece of 

 platinum wire about 4 inches long ; bend one end into a hook 

 and place in the dish so that the hooked end remains out of 

 the liquid, and by hanging on to the edge of the basin prevents 

 the wire from slipping in altogether. This platinum wire is 

 used from time to time to break up the scum and thus assist 

 evaporation. When the whole of the juice is reduced to a 

 stiff paste, place the dish in the steam oven until it ceases to 

 lose weight. This will occupy two or three days, and the dish 

 should be removed to a desiccator at night time, or whenever 

 the oven is allowed to cool. 



187. Soluble Ash.— When the solids in the juice no 

 longer lose weight, the dish is heated very cautiously on an 

 Argand burner, and the ash determined as in a sample of oil 

 cake. Special care must be taken to prevent the charred mass 

 from fusing. 



188. Soluble Albuminoids.— The lactic acid which has 

 been added to the portion measured off for this estimation will 

 precipitate all the albuminoids in a coagulated state. After 

 the liquid has stood twenty-four hours or more, decant off the 

 liquor through a filter paper, arranged with a filter pump as 

 shown in fig. 15. Remove the solid matter with hot water to 

 the paper, and wash well. Dry the precipitate in the steam 

 oven. Place the filter paper with its contents in an 8-oz. flask, 

 and determine the nitrogen by the acid process. 



