148 



Phelps and Weed — Succinic Acid. 



Table II. 

 HC1 value of 



Treat- Differ- 



ment NaOH H a S0 4 NaOH Na 2 S 2 3 Iodine ence 



with solution solution solution to solution solution to in terms 



No. C0 2 used used coloration used coloration of HC1 



min. grm. grm. grm. grm. grm. grm. 



(1) 15 0-1012 0-1306 0-0293 0-0001 + 



(2) 30 0-1012 0-1219 0*0205 0-0002 + 



(3) 15 0-1349 0-1524 0-0172 0-0003 + 



(4) 30 0-1349 0-1568 0*0216 0'0003 + 



(5) 15 0-1012 0-1306 0*0302 0*0013 0*0005 + 



(6) 30 0-1012 0-1306 ._ 0*0302 0*0013 0*0005 + 



(7) 15 0*1349 0*1742 0.0392 0*0004 0*0005 + 



(8) 35 0*1349 0*1742 0*0552 0*0162 0*0003 + 



The differences recorded in the last column of Table II 

 show that the standard of the sulphuric acid is slightly higher 

 than the summation of the sodium hydroxide originally taken, 

 and of the sodium hydroxide or thiosulphate and iodine used 

 to determine the excess of sulphuric acid. From these results 

 it seems to appear that the differences are presumably to be 

 attributed to two causes — the experimental error and, perhaps, 

 a slight mechanical loss of sulphuric acid during the long 

 boiling. 



These results show that a non-volatile acid like sulphuric 

 acid may be used with exactness to determine alkaline carbon- 

 ates in either of the two ways described. The essential thing 

 in the exact titration with a solution of sodium hydroxide, 

 with phenolphthalein as an indicator, as is well known, * is the 

 absence of carbonate, as is also the case in the use of the 

 potassium iodide-iodate mixture. f This condition is easily 

 attained by boiling, as was done in these experiments. 



From these results, it may be seen that the standards of the 

 solutions used in work in iodimetry, alkalimetry, and acidime- 

 try may be found as exactly by titrating against certain pure 

 organic acids as standards, as against the best known standards 

 usually used in such work — the decinormal solution of arsen- 

 ious oxide, or a decinormal solution of hydrochloric acid, 

 standardized gravimetrically as silver chloride. Succinic acid 

 was used as the organic acid standard in this work because of 

 the ease with which it is prepared in a state of purity and its 

 ready solubility in water, but it is clear from work shown in 

 an earlier paper*}: from this laboratory that malonic, benzoic, 

 and phthalic acids as well as the anhydrides of succinic and 

 phthalic acids, could be used with equal exactness. 



*Kuster, Zeitschr. anorg. Chem., xiii, 127. 

 f Groger, Zeitschr. angw. Chem., 1890, 353. 

 J This Journal, xxvi, 138. 



