J. H. Long — Polarization of Tartrate Solutions. 357 



[or], When for 1 molecule of tartrate 1, 2 or 3 molecules of inactive 

 substance are present. 



Formula of salt. 1 mol. 



NaCl 21-86 



NaBr_. 2179 



NaN0 3 21 



Na„S0 4 21 



N"a 2 HP0 4 . 12H 2 0._. 21 



Na 2 S 2 3 . 5H 2 21 



NaH 2 P0 2 . H 2 21 



NaC 2 H 3 2 . 3H 2 .__ 21 



KC1 22 



KBr 22 



KI 22 



KN0 3 22 



KSCy 22 



KC 2 H 3 2 22 



K 2 S0 4 22 



NH 4 Cl..-_ 22 



NH 4 Br 22 



2 mol. 

 21-41 

 21-42 

 21.41 

 20-49 



20-92 



21-16 



22-88 

 2300 

 23-09 

 23-07 

 22*66 

 22-87 



22-67 



22-70 



3 mol. 

 20-99 



21-16 



(For -J* mol. 



= 21-61) 



(For \\ mol. 



= 21-41) 



23-14 



22-82 

 23-25 



22-81 



We see from the above that the specific rotation in presence 

 of two molecules of NaCl, NaBr, NaN0 3 , or one molecule of 

 Na 3 HP0 4 . 12H a O, or one and one-half molecules of NaH a PO a . 

 H 2 is very nearly the same, 21*°41. 



In presence of one molecule of ]STa 9 S0 4 it is a little less, while 

 for NaC a H 3 2 and Na a S a 3 no simple relation is apparent. 



Two molecules of KBr, KC1, KI, KNO, and KC a H 3 O a exert 

 nearly the same influence, one molecule of K a S0 4 gives a 

 smaller value, while KSCy is irregular. 



Roughly, it appears that the potassium salt molecules increase 

 the rotation in about the same proportion that the sodium salts 

 diminish it. The explanation of this may not be immediately 

 apparent. 



Cases similar to those observed in the experiments of Gernez, 

 referred to above, have been explained by the hypothesis of 

 Biot according to which loose combinations are formed between 

 the active and inactive substance having a rotation different 

 from that of the former. Gernez has given the composition of 

 some of these molecular combinations. The case in hand, how- 

 ever, is somewhat different. If we could assume here an action 

 of mass by which on addition of potassium salts the solution 

 would be made to contain neutral potassium tartrate, and on 

 addition of sodium salts neutral sodium tartrate, then the dis- 

 turbance could be partially explained. According to Landolt 

 (Ber., vi, 1073), the specific rotation of neutral potassium tar- 

 trate, calculated as anhydrous, is 28*48, while that of the neutral 

 sodium salt is 30*85. However, if instead of taking equal 



