12 
Potassium Trithionate, K 2 S 3 0 6 . The following are the 
statements regarding the crystalline form of this salt : — 
Gmelin gives two (1) “ Slender four-sided obliquely trun- 
cated prisms (Plessy T. fur Pract. Chem. 33, 348)/’ (2) “Right 
rhombic prisms with dihedral summits resting on the acute 
lateral edges (Provostaye N. Ann. Chim. Phys. 3, 354).” 
According to Watts it forms four-sided prisms, bevelled with 
two faces, and according to Miller it crystallizes in the 
rhombic system, prismatic type with dihedral summits. I 
obtained it in rhombic needles of x P, with the acute edges 
modified by another prism cc P2 ; ooPgo, and x Px are also 
present ; they are terminated by a brachy dome. Some of 
the crystals taper like a sewing needle, I suppose through 
the presence of a very acute pyramid. I find the axes 
to be a : b : c = 0'3586 : T0000 : 0 - 4204, and the observed forms 
are x P, x P2, x Px , x Px , Px . 
Form. 
Angle. 
Found. 
Calculated. 
OoP 
w 
39°31' 
39°28' 
ccP2 
w 
71°12' 
71°18 / 
Px 
w 
45°37' 
45°37' 
This salt is prepared by acting on a saturated solution of 
Potassium thiosulphate with S0 2 . Now, as it is not stated 
that sodium thiosulphate will not similarly yield sodium 
trithionate, nor any reason given why it should not, I at- 
tempted to prepare sodium trithionate in this manner, but 
only obtained crystals of sodium thiosulphate. Rathke 
(Journ. pr. Chem. 95, 13) prepares sodium trithionate as a 
white powder by decomposing Potassium trithionate with 
sodium tartarate. 
