BY R. GREIG-SMITH, 



727 



The method of estimating the chloroform, by decomposing it 

 with alcohohc soda and titrating the chloride with silver nitrate, 

 was employed. After a few trials, the following method was 

 adopted. One hundred grams of soil were put into a 300 c.c. 

 flask, and 100 c.c. of methylated spirit containing 5 c.c. of a 10% 

 alcoholic solution of tartaric acid were added. A Young 1 2-pear, 

 still-head was attached, and the mixture was distilled. Eighty 

 c.c. were generally obtained in from an hour to an hour and a 

 half. The distillate was treated with 5 c.c. of 15% soda (one 

 stick of caustic soda, pure by alcohol, to 100 c.c. of water) and 

 20 c.c. of water, and boiled under an inverted condenser for 10 

 minutes. Three or four drops of phenolphthalein were then 

 added, and the alkali neutralised with nitric acid (10% by 

 volume). After cooling, 1 c.c. of 3% chromate of potash was 

 added, and the solution was titrated with silver nitrate, 8*535 

 grams to 1,000 c.c. (1 c.c. = 2 milligrams of chloroform). 



In the trial-tests, 11*9 milligrams of chloroform were decom- 

 posed with soda, and titrated with 5*95 c.c. of silver nitrate = 11*9 

 milligrams of chloroform. One hundred grams of soil, with no 

 chloroform, required at this time 0*1 c.c. of silver nitrate. One 

 hundred grams of soil distilled with alcohol containing 11-9 

 milligrams of chloroform required 5*9 c.c. silver nitrate =11*8 

 milligrams of chloroform. The method is,, therefore, fairly 

 accurate. 



Experiment i. — A soil containing 8 '8% of moisture was treated 

 overnight with 1*5% of chloroform, and, in the morning, the soil 

 was spread out on paper. In an hour, all odour of the disinfect- 

 ant had disappeared. One hundred grams of soil at this stage 

 gave, upon distillation, 13*9 milligrams of chloroform. After a 

 twenty-four hours' exposure to the air, the moisture fell to 1"6%, 

 and 5*4 milligrams of chloroform were recovered fi-om 100 grams 

 of the soil. After a further 24 hours' exposure to the air, 100 

 grams of the soil yielded 4*2 milligrams of chloroform. 



It is apparent that the bulk of the disinfectant is rapidly 

 volatilised upon exposure to the air, and that a small quantity is 

 held persistently. 



