72 



F. B. GUTHRIE AND A. A. RAMSAY. 



5. Congo red — Fairly sharp. 



6. Lacmoid — Not so sharp on account of the purple trans- 



ition. 



7. Resorcin derivative — Not sharp. 



8. Turmeric — Not good. 



9. Sodium alizarin sulphonate — Very sharp. 



Behaviour of indicators towards mono- and di-basic 

 phosphates. 



Pure mono- and di-basic phosphates of sodium and calcium 

 were prepared according to methods given for the prepar- 

 ation of these salts in Roscoe and Schorlemmer, and in 

 Watts' Dictionary of Chemistry. The following table shows 

 the number of cc. N/10 NaHO or N/10 H 2 S0 4 , which were 

 required to neutralize 0*2 grammes of these respective salts. 





Mono sodium 



Di sodium 



Mono calcium 



Di-calcium 





phosphate 



phosphate 



phosphate 



phosphate 





NaH 2 P0 4 



Na 2 HP0 4 



CaH 4 (P0 4 ) 3 



Ca 2 H 2 (P0 4 ) 3 





*2 grms. 



"2 grms. 



•2 grms. 



"2 grms. 



Methyl orange 



•648 



6535 



•448 



8-747 



Phenol phthalein . . . 



13-851 



•402 



17-937 



•498 



Cochineal ... 



•607 



6-495 



•349 



8-747 



Litmus 



1-697 



6535 



1*395 



1-548 



Congo red ... 



•678 



6636 



2-491 



2-916 



Lacmoid ... 



•697 



6-535 



1-196 



7943 



Resorcin derivative 



•607 



6736 



2-192 



11-965 



Turmeric ... 



15-146 





18-136 



•498 



Sodium alizarin 











sulphonate 



•349 



4-323 



•149 



9351 



The heavy black figures represent the number of cc. of 

 decinormal acid, those in ordinary type of decinormal alkali 

 required to neutralize *2 grms of the respective salts. 



The strength of the solutions operated on were 10 

 grammes in 1000 cc. water, 20 cc. being taken for titration.' 

 Since superphosphate of lime is stated 1 to be soluble without 

 decomposition only in dilute solutions, a solution containing 

 2*5 grammes per litre was employed in this case (roW atomic 

 solution). 



1 Watts' Dictionary of Chemistry, Vol. iv, p. 109. 



