158 



AGRICULTURAL CHEMISTRY 



Fig. 65. 



moved. Dry matter, as the term implies, is the dry ma- 

 terial free from all traces of hydroscopic moisture, and 

 the amount is determined by subtracting the per cent, of 

 water from 100. For example, if flour contains 12 per cent, 

 water there will be 88 per cent, of dry matter. The amount 

 of dry matter in substances ranges between wide limits as 7 

 per cent, and less in some fruits to 99 per cent, in sugar. 

 Experiment 36. Determination of water in potato. Carefully 

 weigh an aluminum dish (Fig. 65). Cut 

 thin slices from different parts of a 

 potato and reduce them to i/8-inch 

 cubes. Weigh in the dish, some of 

 these pieces, forming a layer not more 

 than two deep. Record the weight, 

 place in the dish a small piece of paper with your initials, 

 then set the dish in the water-oven 

 (Fig. 62), and allow it to remain 

 twenty-four hours, or until the next 

 exercise. After drying, weigh again, 

 and from the loss of weight calculate 

 the per cent, of water in the potato. 

 (Weight of potato and dish before dry- 

 ing, minus weight of potato and dish 

 after drying, equals weight of water 

 lost. Weight of water divided by weight 

 of potato taken, multiplied by 100, 

 equals the per cent, of water in the 

 potato. ) 



Experiment j/. Water in flour. 

 In the same manner, determine the 

 per cent, of water in flour, using about 

 Fi g- 66 - 2 grams of flour, and noting the ex- 



act weight before and after drying. 



Experiment 38. Water in milk. Weigh a watch-glass and place 

 it on the water-bath (see Fig. 66). Measure with a pipette 3 cc. of 

 milk into the watch-glass. Evaporate to dryness on the water-bath, 



