160 MR. H. BAKER ON SOME THIONATES. 



the acute lateral edges '' (Provostaye, N. Ann. Chim. Phys. 

 iii. 354) . According to Watts, it forms four-sided prisms, 

 bevelled with two faces ; and according to Miller, it crys- 

 tallizes in the rhombic system, prismatic type with dihedral 

 summits. I obtained it in rhombic needles of o^P, with 

 the acute edges modified by another prism oc^2. 00^00 

 and 00^00 ^^'6 also present; they are terminated by a 

 brachydome. 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 « : 6 ; ^ = 0-3586 : i-oooo 

 : 0*4204 ; and the observed forms are oc^^ 00^2, 00^*00 > 



This salt is prepared by acting on a saturated solution 

 of potassium thiosulphate with SO^. Now, as it is not 

 stated that sodium thiosulphate will not similarly yield so- 

 dium trithionate, nor any reason given why it should not, 

 I attempted to prepare sodium trithionate in this manner, 

 but only obtained crystals of sodium thiosulphate. Ratlike 

 (Journ. pr. Chem. xcv. 13) prepares sodium trithionate as 

 a white powder by decomposing potassium trithionate with 

 sodium tartrate. 



