Phelps and Weed — Succinic Acid. 145 



mately decinormal, and against pure succinic acid, in the 

 manner described in the paper to which reference has been 

 made. The exact standard of the decinormal solution of sul- 

 phuric acid was determined by titration against the decinormal 

 sodium hydroxide solution, in presence of phenolphthalein as 

 indicator. 



The decinormal solution of arsenious oxide was carefully made 

 up by treating 4 9500 grams of the purest arsenious oxide of 

 commerce, twice sublimed, in a beaker in fifty cubic centi- 

 meters of distilled water with fifty cubic centimeters of a 

 solution containing about twelve grams of sodium hydroxide, 

 prepared pure according to the method of Krister.* After the 

 arsenious oxide had been dissolved by gentle warming, the 

 solution was transferred to a standardized liter flask, by using 

 enough distilled water in this transference to make the volume 

 approximately 250 cubic centimeters. This was then satu- 

 rated with purified carbon dioxide and diluted to a liter under 

 proper conditions of temperature. The solution of iodine was 

 made up approximately decinormal by dissolving iodine in an 

 aqueous solution of potassium iodide, the exact strength of the 

 solution being determined by titration against the standard 

 solution of decinormal arsenious oxide, in presence of an excess 

 of sodium bicarbonate, with starch solution made in the usual 

 way as the indicator. The solution of sodium thiosulphate 

 was made up approximately decinormal by dissolving in dis- 

 tilled water the pure sodium thiosulphate of commerce. The 

 exact strength of this solution was determined by titrating 

 definite portions of it against the iodine solution, using the 

 starch solution as indicator. 



In this work, potassium iodide and potassium ioclate were 

 first put into solution in such amounts as to be in excess at the 

 end of the reaction. Definite portions of the decinormal 

 hydrochloric acid solution were then run in from a burette, 

 setting free the iodine. The solution of sodium thiosulphate 

 was next added in amount slightly in excess, and this excess 

 was determined either by adding more of the hydrochloric 

 acid solution or by the addition of the iodine solution, until 

 the blue color of the starch indicator showed the reaction to be 

 complete. In all of the experiments recorded in Table I, one 

 gram of potassium iodide was used and fifty cubic centimeters 

 of a solution of potassium iodate, prepared by dissolving 3*3400 

 grams of the iodate in a liter of distilled water. Presumably 

 on account of the presence of acid potassium iodate in the 

 sample of iodate used, the addition of the potassium iodate 

 solution to the potassium iodide set free a slight amount of 

 iodine. This free iodine was removed either by boiling until 



* Loc. cit. 



