76 PROVISIONAL METHODS FOR ANALYSIS OF FOODS. 



about 4 or 5 grams of freshly ignited asbestos to absorb it; dry for from 20 to 24 

 hours in a water-jacketed oven. a If care is taken in measuring, this method will 

 be found to be as accurate as weighing. In case of jellies that contain starch or 

 insoluble matter, solids may be determined as directed below under (b) . 



(2) By calculation from specific gravity. Determine the specific gravity of the solu- 

 tion of jelly or diluted sirup, or of the juice, by means of a Westphal balance, picno- 

 meter, or specific-gravity spindle, and calculate the solids from Table IV. b 



(b) IN FRESH FRUITS, JAMS, MARMALADES, PRESERVES, AND CANNED GOODS. 



Weigh about 20 grams of pulped fresh fruit, or such an amount of fruit products as 

 will give not more than 3 to 4 grams of dried material, into a large flat-bottomed 

 dish containing ignited asbestos; add a few cubic centimeters of water, mix 

 thoroughly, and dry as in [(a) 1]. 



4. DETERMINATION OF INSOLUBLE SOLIDS. 

 (a) KREMLA'S METHOD MODIFIED. 



Weigh 50 grams of the sample; transfer by the aid of warm water to a mortar and 

 thoroughly macerate, c then transfer to a muslin filter and wash thoroughly with 

 warm water, care being taken at each addition of water to thoroughly stir the pulp. 

 Collect the filtrate in a 500-cc flask, cool and make up to volume. Usually this 

 amount is sufficient to remove all soluble material. In extreme cases increase the 

 washings to 1000 cc: transfer the insoluble residue to an evaporating dish, dry, and 

 weigh. 



(b) GERMAN OFFICIAL METHOD. 



Transfer a weighed portion of the fruit product to a graduated flask, add water, 

 shake thoroughly and make up to volume. Allow this to settle and either filter or 

 decant off the supernatant liquid. Take an aliquot for the determination of soluble 

 solids. Total solids less soluble solids equals insoluble solids. The fruit must be 

 thoroughly macerated and the use of a mechanical shaker would be advisable. 



5. DETERMINATION OF ALCOHOL. 



Determine alcohol in 50 grams of the original material according to the method 

 prescribed on page 82. 



6. DETERMINATION OF ASH. 



Evaporate to dryness 50 cc of the solution of jelly or diluted sirup [see 2 (a)], 25 

 grams of juice or fresh fruit, or 10 grams of jam, marmalade, preserves, or canned 

 fruit in a large platinum dish; then thoroughly char at as low a heat as possible, 

 extract with water, filter, and wash. Return the filter paper and insoluble material 

 to the dish and thoroughly ignite; add the soluble portion and evaporate the whole 

 to dry ness after add ing a few cubic centimeters of a solution of ammonium carbonate; 

 then heat for a moment to very low redness; cool in a desiccator and weigh. The 

 weighing must be made as quickly as possible, as the ash absorbs moisture very 

 rapidly. 



A. McGill, Laboratory of Internal Revenue, Ottawa, Canada, has devised a forced draft water oven 

 for drying at temperatures between CO and 90 C. The oven is heated by means of ordinary gas burn- 

 ers, and the temperature is controlled by introducing at the bottom of the oven a blast of air from a 

 blower run by a small water motor. Before discharging into the oven the air tube enters the water 

 chamber and is coiled a number of times in order to sufficiently warm the water before it enters the 

 oven. The exit end of the air tube is covered with a concave-convex disc in order to distribute the 

 blast and to prevent harmful currents. By regulating the burners and the flow of air a fairly con- 

 stant temperature can be obtained. The bottom of the oven is curved instead of flat, to prevent 

 bumping when the water is boiling; a perforated plate serves as a false bottom. 



>Ztschr. Nahr. Hyg. Wtuir. 1892, 6, 483. 



c McGill, by letter, recommends the use of a mechanical shaker to obtain complete solution of the 

 soluble material. 



