224 
IOWA ACADEMY OP SCIENCE 
The value of HCl in 1 cc. of the hydrochloric acid solution 
is .0036494. 
To summarize, we have the concentration of the solution of 
hydrochloric acid determined by five different methods and 
standards. The first three are of undoubted accuracy, though 
the method of Hulett and Bonner has the disadvantage that 
neither the boiling point of hydrochloric acid nor the distillate 
is perfectly constant at any concentration, though very nearly 
so. With these three old methods the acid phthalates are com- 
pared. The following are the concentrations for 2 cc., found by 
the different methods : 
1. Method of Hulett and Bonner 0036470 
2. Silver chloride 0036497 
3. Benzoic acid, series I and II 0036502 
4. Acid Potassium Phthalate, series I and II 0036490 
5. Acid Sodium Phthalate 0036494 
It will be seen that these results agree within the limits of 
ordinary volumetric work. Leaving out the method of Hulett 
and Bonner whose slight defect has been mentioned and was 
fully recognized by its founders in their original publication,^ 
the other results are almost identical. 
From this study it would seem that benzoic acid, acid potas- 
sium phthalate and dehydrated acid sodium phthalate may with 
equal confidence be used as standards. The acid phthalates have 
the advantage of much higher equivalent weights, ready solu- 
bility in water and ease of preparation in the pure state. 
Laboratory of Grinnell College. 
