MR. H. BAKER ON SOME THIONATES. 159 



Form. Angle. Calculated. Found. Gmelin. 



O / O I O I 



P A 126 47 126 51 127 



B 126 6 125 55 126 



C 79 9 79 8 79 10 



P| A 89 54 89 58 90 12 



C 104 58 104 52 



_OoP W 89 20 89 22 89 8 



Poo W 60 54 61 I 



Silver Sodium Dithionate, (AgNa)jSj,06,2Aq, is, accord- 

 ing to Watts, " apparently isomorphous with the compo- 

 nent salts." I find it to be rhombic with the axes d : b : 

 c = o-98i3 : 1*0000 : 0-5856, and the forms Pqo , P, ^^^V^ , 

 QQ P, ooPqo • 1'^6 dome is developed so much as to make 

 the crystals horizontally prismatic j the prism is only 

 slightly developed ; and the pyramid P| does not occur. 

 Watts also says it " exhibits very distinct cleavage;''^ this 

 cleavage-plane I find to be 00^^ ', ^-nd I also find that the 

 sodium and the silver dithionates exhibit very distinctly 

 this cleavage. 



This sample contains "/o Ag 32*0. 

 AgNaSi06,2Aq requires Vo Ag 33"0o. 



Potassium Trithionate, K^SjOg. — The following are the 

 statements regarding the crystalline form of this salt : — 

 Gmelin gives two : — (i) "slender, four-sided, obliquely trun- 

 cated prisms" (Plessy, J.fiir pract. Chem.xxxiii.p.348); (2) 

 "right rhombic prisms with dihedral summits resting on 



