94 
Ionic  Dissociation. 
(Am.  Jour.  Pharm. 
(     February,  1920. 
2.  Rapidity,  where  a  large  number  of  determinations  are  to  be 
made. 
3.  Non-interference  of  color  or  precipitate. 
4.  Sharp  end-points  are  usually  obtained. 
5.  Little  or  no  chemical  training  is  needed  on  the  part  of  the 
operator. 
Other  determinations  that  have  been  made  with  apparatus  based 
upon  conductivity  are:  Magnesium  in  presence  of  calcium,  ferrous 
iron  in  presence  of  ferric  iron,  patent  flour  in  admixture  with  straight 
flour  and  "red  dog,"  the  solubility  of  sparingly  soluble  salts  (such 
as  the  haloid  salts  of  silver,  barium  sulphate,  lead  sulphate,  etc.), 
the  hydrolysis  of  weak  acids  and  weak  bases.  Conductivity  methods 
of  analysis  are  relatively  new  but,  as  they  become  better  known, 
promise  to  supplant  many  of  the  older  and  slower  methods  of  gravi- 
metric and  volumetric  analysis,  particularly  in  laboratories  connected 
with  industrial  establishments.  Several  firms  are  now  supplying 
complete  apparatus  for  special  kinds  of  determinations,  and  im- 
provements are  being  constantly  made  on  what  first  appeared  on 
the  market. 
BIBLIOGRAPHY. 
Loomis  and  Acree:  "Study  of  Hydrogen  Electrode,  Calomel  Electrode 
and  Contact  Potential,"  Am.  Chem.  Jour.,  46:  585,  191 1. 
Loomis  and  Acree:    "Extensive  Bibliography,"  Ibid.,  46:  621,  191 1. 
McClendon:  "New  Hydrogen  Electrode,"  Am.  Jour,  of  Physiol.,  38:  2, 
1915. 
Walpole:    "Gas  Electrode  for  General  Use,"  Biochem.  Jour.,  7:  410,  1913. 
Walpole:    "Improved  Hydrogen  Electrode,"  Ibid.,  8:  131,  1914. 
"Theory  and  Apparatus,"  Catalogue  70  and  Bulletin  701,  1919.  Leeds  and 
Northrup,  Philadelphia. 
Hildebrand:  "Some  Applications  of  the  Hydrogen  Electrode  in  Analysis," 
Jour.  Am.  Chem.  Soc,  35:  847,  1913. 
Harned:  "Hydrogen-  and  Hydroxyl-ion  Activities  of  Solutions  of  HCl, 
NaOH  and  KOH,"  Ibid.,  37:  2460,  19 15. 
Kelley  and  Conant:  "Determination  of  Vanadium  by  Electrometric 
Titration," 38:  341,  1916. 
Ellis:    "Preparation  of  Calomel  Cell,"  Ibid.,  38:  737,  1916. 
Long:    "Simple  Cell  for  H-ion  Determination,"  Ibid.,  38:  936,  1916. 
Hostetter  and  Roberts:  "Electrometric  Titrations,  with  Special  Reference 
to  Ferrous  in  Ferric  Solutions,"  Ibid.,  41 :  1337,  1919. 
Roberts:  "Apparatus  for  Use  in  Electrometric  Titrations,"  Ihid.,  41: 
1358,  1919- 
