12 FRUITS AND FRUIT PRODUCTS. 



su^ar, as it has been shown '^ that levulose is dehydrated at 100° C. 

 Of the other two methods employed the one depending upon the cal- 

 culation of solids from the specific gravity of the 20 per cent solution 

 gives results more nearly concordant with drying in vacuo than by 

 drying at 100° C. , the results being from 1 to 1.50 per cent higher than 

 those obtained with the latter method. With pure jellies the specific 

 gravity method gives very satisfactory results, but with glucose prod- 

 ucts containing large amounts of dextrin and with jellies containing 

 soluble starch this method is not so reliable. For the purpose of 

 obtaining comparative results with all classes of fruits and fruit prod- 

 ucts and with the different grades of goods the method of drying at 

 100° C. for from twenty to twenty-four hours is considered satisfactory. 

 The method is an empirical one and all details must be followed closely 

 in order to obtain comparative results. When neither sand nor asbes- 

 tos was used as an absorbent the results were unsatisfactory and from 

 2 to 3 per cent too high. 



IN JUICES AND JELLIES.^ 



By direct determination. — Measure 25 cc of a 20 per cent solution 

 of jelly, or weigh 25 grams of juice into a large flat-bottomed dish 

 which contains about tt or 5 grams of freshly ignited asbestos to absorb 

 it; dry for from twenty to twenty-four hours*" in a water- jacketed oven. 

 If care is taken, measuring will be found to be as accurate as weighing, 

 but the pipette must be graduated to deliver 25 cc of a 20 per cent 

 sugar solution. In the case of jellies that contain starch or other 

 insoluble matter solids may be determined as directed under fresh 

 fruits, jams, marmalades, etc. 



By calcidation from specific gravity. — Determine the specific gravity 

 of the solution of jelly, or of the juice, by means of a Westphal 

 balance, pycnometer, or specific-gravity spindle, and calculate the 

 solids from the table given in bulletin 65. 



IN FRESH FRUITS, JAMS, MARMALADES, PRESERVES, AND CANNED FRUITS. 



Place a weighed quantity of about 20 grams of pulped fresh fruit, 

 or such an amount of fruit product as will give not more than 3 or 4 

 grams of dried material, in a large flat-bottomed dish containing from 

 4 to 5 grams of ignited asbestos; add a few cubic centimeters of water, 

 mix thoroughly, and dry as under "Direct determination" in "Juices 

 and jellies." 



^Carr and Sanborn, U. S. Dept. of Agric, Div. of Chem. Bull. 47, p. 134. 



"McGill by letter recommends the use of the Macfarlane tube described in the 

 Analyst, 1893, 18, 73, for the determination of total solids in substances containing 

 large amounts of sugar. 



<= Wiley, Principles and Practice of Agricultural Analysis, vol. 3, p. 579, recom- 

 mends drying first at a low temperature and completing the operation at 100° C. or a 

 little higher. 



