144 Phelps and Weed— Succinic Acid. 



The practical difficulty usually found in the use of arsenious 

 oxide as a standard in iodimetry lies, in our experience, in the 

 fact that in most cases the purest resublimed arsenious oxide 

 does not always give a clear solution when treated with an 

 alkaline hydroxide or bicarbonate. To whatever cause this 

 insoluble residue may be due — to a slight action of the alkaline 

 solution upon the glass or to some impurity in the alkaline 

 hydroxide or bicarbonate used — it is in itself sufficient to make 

 desirable, for accurate work, the possibility of checking results 

 obtained with arsenious oxide as a standard. 



It has been shown in former papers* from this laboratory 

 that succinic acid may be used, in presence of cochineal as an 

 indicator, as a standard for the exact determination of a deci- 

 normal solution of ammonium hydroxide, and, also, . that 

 succinic, malonic, benzoic, and phthalic acids, as well as the 

 anhydrides of succinic and phthalic acids, may also be used, 

 with phenolpthalein as an indicator, as standards for decinor- 

 mal solutions of sodium hydroxide and of barium hydroxide. 

 The results, which are given below, show that succinic acid 

 may also be used as the standard for work in iodimetry, alka- 

 limetry, and acidimetry, with exactly as much accuracy as the 

 best previous standards for this work — titration against a 

 decinormal solution of pure arsenious oxide or the gravimetric 

 determination of a solution of hydrochloric acid as silver 

 chloride. 



For this work, solutions of hydrochloric acid and of sul- 

 phuric acid were made up approximately decinormal by 

 diluting in the usual way the chemically pure acids of com- 

 merce. The exact strength of the hydrochloric acid solution 

 was determined by precipitating definite amounts of the solu- 

 tion of hydrochloric acid, in some cases, in a platinum dish 

 and, in other cases, in a glass beaker as silver chloride by an 

 excess of silver nitrate in the presence of a few drops of dilute 

 nitric acid, filtering off on asbestos under pressure in a per- 

 forated platinum crucible the precipitate of silver chloride 

 after allowing the whole to stand in the dark twenty-four 

 hours. The solution of sodium hydroxide was prepared by 

 diluting pure sodium hydroxide, prepared by the method, 

 given by Kuster,f with distilled water, freshly boiled. The 

 solution of sodium hydroxide was kept in a closed bottle, 

 connected in the usual manner with a three-way-stoppered 

 burette. It was protected from the action of carbon dioxide 

 in the air by soda lime tubes. The exact strength of this 

 approximately decinormal solution was determined by titration 

 against the standard solution of hydrochloric acid, approxi- 



* This Journal, xxiii. 211 ; xxvi, 138. 

 f Zeitschr. anorg. Chem. xli, 474. 



