1912] Lipman-Slwrp: Phenoldisulphonic Acid Method 33 



It is evident from Table VIII that the chlorine and not the 

 base is the interfering element, and while the amounts of chlorine 

 were not so proportioned as to be equivalent in the case of the 

 two monovalent bases, the effect is clearly seen of the smallest 

 and the largest amounts of chlorine present in the salts, which 

 can be calculated from the molecular weights. The negative 

 ion therefore seems to be the active agent in setting free nitric 

 acid, but the decreases, depending as they do on other conditions 

 such as evaporation on the water bath and length of exposure, do 

 not take place in accordance with any definite law. 



The last phase of the salt effects studied was that above re- 

 ferred to in the discussion of Tables I. II, and III, namely, the 

 reason for differences in the action of NaoCOj and Na2S04 on 

 nitrate-containing material. Since it was evident that NaoCO, 

 should react similarly to Na^SO^ when the phenoldisulphonic 

 acid was added to the dried residue to be analyzed, we suspected 

 that the losses occurring when NajSO^ was employed came about 

 on the water bath in evaporating the solution, under which con- 

 ditions only, according to our work, could there have been a 

 difference in the action of the two salts. 



The results given in the following table prove that our sus- 

 picions were well founded. In this series the dry salts were 

 thoroughly mixed with the nitrate-containing residue obtained by 

 evaporating standard nitrate solutions, and then the phenoldi- 

 sulphonic acid reagent was added. NaCl was similarly tested. 



