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METHOD OF DETERMINING THE SPECIFIC GRAVITY 

 OF SOLUBLE SALTS BY DISPLACEMENT IN THEIR OWN 

 MOTHER-LIQUOR; AND ITS APPLICATION IN THE CASE 

 OF THE ALKALINE HALIDES. [From The American 



Journal of Science, Vol. xxi. January, 1906] . . . 197 



This research was suggested by the meteorological 

 conditions of the summer of the year 1904. The great 

 anticyclone which persisted over northern Europe 

 during the months of July and August of that year pro- 

 duced tropical conditions which were evidenced alike by 

 the high temperature of the air and by its insignificant 

 diurnal variation. My hydrometric observations which 

 demand a constant temperature of 19-5 C. were put a 

 stop to by these conditions. 



The very narrow limits of the diurnal variation of 

 temperature suggested the realization of a long con- 

 templated method of determination of specific gravity, 

 namely, that of soluble salts by displacement in their 

 own mother-liquor. I took it up at first merely as a 

 tour de force in experimentation with which to occupy 

 myself during the hot weather, but it turned out to be a 

 luable method of research, and the duration of the 



II <>f hot weather enabled me to prove and to use it. 



Fundamental principle of the method. 

 There is one liquid in which every soluble salt is 

 quite insoluble, and that is its own mother-liquor at the 



nperature at which the one parted from the other . 198 

 By immersing the salt in its own mother-liquor at 

 that temperature and by making the maintenance of 

 this temperature a conditio sine qua non of every 

 manipulation during which the two are brought to- 

 gether again, errors due to uncertain solubility are 

 initiated, and contamination of valuable preparations 



led. 



It . y the immersion of cadi salt in its 



n mother-liquor that iN di>pla< ement i^ determined, 



nd.ined with the M nd the 



specific gravity <>f the m.th< -r -liquor, gives the specific 



gr dt. 



who |in. POM- d must 



d dilht ulties whi< h he will 



ikr Mich HUM 'ICC 



,ine the; !p him. 



