OP ARTS AND SCIENCES. T 



lowing crystallograpliic measurements of the crystals whose formation 

 and reactions we have described. 



Angles betioeen normals. 



(Ill) A (100) 70° 19J' 



(111) A (TTl) 70° 17' 



a:b:c = \: 1.38G : 0.571 



The pinacoid planes were irregular and the angles can only be 

 regarded as approximate. 



System Trimetric with hemihedral habit. 



Observed planes + K- {111} {100} {110} {Oil}? 



In the following table the crystallographic ratios are compared with 

 those of the acid tartrates of rubidium, cresium and potassium, formerly 

 measured by us, and which have the same general form and hemihedral 

 habit. 



Vertical. 



Acid tartrate of csesium . . . 0.661 



'• " rubidium . . . 0.695 



" " potassium. . . 0.737 



Silver emetic 0.412 



III. Ox THE Solubility op Argentic Chlokide in "Water. 



In our analyses of antimonious chloride we constantly noticed, 

 while washing the precij^itated chloride of silver with warm water, 

 that although the water first decanted from the precijsitate was per- 

 fectly clear it became turbid when mixed with the successive wash- 

 ings ; and on investigating the cause of this unexpected result we 

 found that it was due to the chloride silver dissolved by the pure wash 

 water and reprecipitated by die excess of nitrate of silver in the filtrate. 

 As the solvent action of tlie water used for washing the precipitate 

 evidently pi'oduced a marked effect on our chlorine determination, we 

 determined at once to investigate the extent of the influence. 



This subject has already been studied by Stas, whose observations 

 are summed up by Dr. John Percy * in his recent volume on the 

 Metallurgy of Silver in the following words : — 



* ^Metallurgy of Silver and Gold, Part I. p. 60. 



