T H E J O U R N A L O F I N D U S T R I A L A N D ELVGINEERIATrGC H E M I S T R E -
406
TABLEI1 Results in Mg. Oxygen Consumed per 1013 cc. Water 1 Hour-85‘ KbfnOa Solution: 15 cc. 2 0 c c . 25 cc. 30 cc. 5 Gelatine ........................ 0.552 0.697 0 . 8 2 1 0 . 8 7 2 5 Dried Egg Alb.. . . . . . . . . . . . . . . . . 1.100 1.293 1.425 1.526 5 Dried Milk . . 1.500 1.850 2.142 2.336 1 . 5 8 8 1.786 Sewage No. 2. .................... 1.228 1.415 1 . 5 3 0 1.655 Sewage No. 3 ..................... 1.082 1.280 1.422 1.605 City t a p water. . . . . 0.372 0.440 0 461 0.482 3 Hours-37 5 G e l a t i n e . . ..... 0.100 0.103 0 . 1 0 8 0.123 0.549 0.539 0.565 0.618 0.490 0.494 S e w a g e N o . 1 . .................... 0 . 4 2 6 0 . 4 5 2 0 . 4 4 4 0.459 Sewage No. 2 ..................... 0.435 0 , 4 6 0 0.440 0 . 4 7 3 Sewage No. 3 . . . . . . . . . . . 0.455 0 , 6 3 3 0 . 4 9 0 0.482 City tap w a t e r . . . . . . . . . . . . . . . . . . . . 0 . 1 5 5 0 . 1 6 0 0.162 0.178
40 cc. 0,952 1.790 ‘2.706 2.094 1.730 1.675 0 527 0.140 0.670 0.477 0,431 0.453 0.473 0.182
difference in this respect. This makes i t quite clear t h a t in comparing results of oxygen consumed a t high temperatures, only those results can be compared t h a t are obtained by a method in which t h e same amount of permanganate is used for t h e oxidation. This is a very important point. However, a t 3 7 O , the amount of K M n 0 4 used for t h e oxidation plays n o large part a n d hence such results can be compared no matter whether or not t h e same amount of permanganate is used. Although the presence of chlorides interferes with t h e determination of oxygen required in acid solution, the 37’ acid solution method of Thresh seems best. T h e chlorides can be readily removed b y AgzO and hence offer no great difficulty. CITY
HEALTI
