496 IOWA ACADEMY OF SCIENCE Vol. XXV, 1918 



2. Organic siihstances with liiuh ash content often contain 

 iron or some other interfering element, whicli ought to be elimi 

 nated before relialble results can be obtained. According to the 

 author's experiences, filtration at this point did not altogether 

 eliminate the interfering action of ash. When, however, the so- 

 dium hydroxide fusion melt was taken up with hot water, a few 

 grams of sodium bicarbonate (CP.) and some talc added, 

 brought to boiling and kept 'boiling for a few minutes, set aside 

 for two hours and filtered, the filtrate was free from interfering 

 basic elements. 



3. In. acidifying the above filtrate with 85 per cent sirupv 

 phosphoric acid, the author's experience was well in accord with 

 Forbes, Beegle, and others, who found that one or two drops of 

 phosphoric acid in excess was insufficient to assure expulsion of 

 all bromine. An addition of even one and a half to two cubic 

 centimeters in excess would boil off all of the bromine witliout 

 causing any loss of iodine. This was sho\Mi by taking an aliquot 

 CI accurately standardized alcoholic solution of iodoform and 

 estimating iodine according to Kendall's method. No loss of 

 iodine occurred when two cubic centimeters of acid was added in 

 excess. 



4. In boiling off the bromine it was made a practice to dilute 

 the filtrate to over 400 cu'bic centimeters and boil down to 25(i 

 cu!bie centimeters, thus assuring a complete expulsion of bromine. 



Under the conditions specified in this short note the author 

 found the method applicable for tankage, roughage and other oi'- 

 ganic substances with a high percentage of ash. 



Chemistry Section, 



Agricultural Experiment Station, 



■•Bulletin 299, Ohio Agr. Exp. Sta., p. 422. 



