ACID POTASSIUM AND ACID SODIUM PHTHALATES 217 
ACID POTASSIUM AND ACID SODIUM PHTHALATES 
AS STANDARDS IN ALKALIMETRY AND 
ACIDIMETRY. 
W. S. HENDRIXSON. 
Quite recently Francis D. Dod^e^ suggested acid potassium 
phthalate and acid sodium phthalate as standards in alkalimetry 
and acidimetry. His paper contains no analytical data and is 
largely theoretical, and so far as the witer can determine no 
such data are available. The two substances have certain very 
desirable features as standards, which Dodge has pointed out. 
The question is whether they are true acid salts. It seemed to 
me a matter of interest to subject them to a somewhat rigorous 
examination \o determine whether they can be relied upon to 
give accurate results in standardization. 
The primary solution used in the study of the acid phthalates 
was an approximately tenth normal solution of hydrochloric 
acid. It was made up according to the method of Hulett and 
Bonner,^ and its concentration was further determined by means 
of silver chloride, and by comparison with two samples of ben- 
zoic acid, one made from the pure commercial acid and the 
other the standard benzoic acid from the Bureau of Standards. 
Solution of Hydrochloric Acid. — Concentrated, chemically 
pure hydrochloric acid was distilled from a glass stoppered dis- 
tilling flask till three-fourths of it had passed over. The dis- 
tillate was then collected in a bottle placed in ice water. The 
end of the condenser tube extended well into the bottle. About 
three-fourths of what remained in the flask was distilled. The 
distillation was not interrupted from first to last, and bumping 
was controlled with platinum scrap. 
The pressure being 740, according to Hulett and Bonner 
17.9745 grams of this latter distillate should contain one mole, 
of HCl, (air weight). The amount weighed from a weight buret 
was 53.997 grams and it was made up to 3.00408 liters with pure 
water, by using the content, not the delivery of three calibrated 
liter flasks, whose total capacity was 3.0004 true liters as cali- 
iJournal of Engineering and Industrial Chemistry, Vol. 7, p. 29. 
^Journal of the American Chemical Society, Vol. 31, p. 393. 
