104 Studies on Solution. 



The organic salts used in this investigation were prepared by adding 

 the necessary amount of sodium ethylate in absolute alcohol to the 

 organic acid in alcoholic solution, as advised by Goldschmidt and pre- 

 viously mentioned in the historical section (page 100). The acids 

 employed were taken from the various samples purified in the work of 

 Lloyd, Wiesel, and Jones. When such were lacking new material was 

 obtained from well-known firms and purified in the following man- 

 ner : Whenever possible the acid was recrystallized from hot absolute- 

 alcoholic solution, but when necessary a small amount of water was 

 added. In every case the fractionation was carried out several times. 

 The halogen-substituted aliphatic acids were fractionally crystallized 

 from hot benzol, placed in a sulphuric-acid desiccator, and the final 

 traces of benzol were removed by introducing into the container pieces 

 of paraffine, which acted as an absorbent for the solvent. To purify the 

 liquid aliphatic acids we resorted to both fractional crystallization by 

 means of a refrigerant and repeated distillations under reduced pres- 

 sure, in the latter case collecting the various fractions in a specially 

 constructed receiver for small quantities. 



The ethylate was prepared as needed in the following manner, as 

 suggested by J. H. Shrader: 1 A special grade of metallic sodium, free 

 from other metals, was wiped carefully with filter paper, the approx- 

 imate amount was pared to fresh surfaces, and in small pieces was 

 put first in a good grade of alcohol, then transferred into some conduc- 

 tivity alcohol for final washing, and finally dropped into a measuring 

 flask of the best alcohol, so that upon solution it could be made up 

 to the mark. With practice it was possible to estimate successfully 

 the amount of sodium to produce a nearly N/10 solution. This 

 solution was standardized and used within an hour or two for the salt 

 preparation. It was found necessary to use the ethylate immediately, 

 as evidences of decomposition giving a straw color to the solution 

 appeared within 24 hours of its preparation, and even sooner in the case 

 of more concentrated solutions. 



This ethylate solution was immediately standardized by means of an 

 N/10 aqueous solution of hydrochloric acid. This latter reagent was 

 prepared by the method of Hulett and Bonner, 2 lately extended by 

 Hendrixson. 3 As a check on this solution four series of silver chloride 

 gravimetric analyses were made at various times throughout the year, 

 none of which varied more than 0.1 per cent. 



Phenolphthalein served as the indicator for the various tit rat ions, 

 special precautions noted in a later paragraph being used to prevent 

 the interference of carbon dioxide from the atmosphere. As a final 

 proof of the correctness of our choice of indicators, the ethylate was 

 standardized with hydrochloric acid, using in this case methyl red as 



1 J. H. Shrader: Dissertation, Johns Hopkins University 14-16 (191.3). 



2 Journ. Amer. Chem. Soc. 31, 390 (1909). Mourn. Amer. Chem. Soc. 37, 2352 (1915). 



