464 PROFESSOR W. DTTTMAR ON THE BEHAVIOUR OF THE 



slightly alkaline with more baryta. The precipitate was allowed to settle, washed, and 

 dried. After a preliminary trial 7 '8 6 grm. of the sulphate of rubidium were dissolved 

 in about 400 c.c. of hot water. 6'6 grm. of oxalate of baryta were now added, and the 

 mixture was allowed to stand for three hours with frequent agitation. As soluble 

 sulphate was still present, the precipitate was filtered off, and some more of the oxalate 

 added, which removed the whole of the S0 3 in other two hours. The filtered solution was 

 evaporated to dryness and ignited gently in platinum. The residue was dissolved in 

 water, a small precipitate (BaC0 3 ) filtered off, and the clear solution again evaporated to 

 dryness in platinum and ignited. The total quantity of carbonate obtained in this and 

 the preceding pioneering operations amounted to about 10 grm. Of this small supply 

 more than one-fifth was lost in the first experiment. 



Experiment I. — 2*04 grm. of carbonate of rubidium were placed in the gas-crucible, 

 and heated in a current of hydrogen over the blowpipe for one hour. When the 

 crucible was opened, it was found to be empty : all the salt had volatilised ! 



Experiment II. — Seeing that the rubidium salt is so very volatile I took care this 

 time to substitute an ordinary Bunsen for the blowpipe. About 2 grm. of the carbonate 

 were operated upon, and the heating in hydrogen continued for one hour. The aspect of 

 the residue showed that the salt had been in a state of fusion. For the analysis of the 

 product, 1*4336 grm. of it were decomposed with hydrochloric acid in the usual apparatus, 

 and the C0 2 collected and weighed. It amounted to 0*2561 grm. or 17 "864 per cent, of 

 the substance analysed. The chloride solution produced was evaporated, finally in a 

 small platinum basin and the residue dried at 150° for two hours; the salt was then 

 moistened with water and again dried at 150°, to expel the uncombined hydrochloric 

 acid, and the drying process continued until the weight of the residue was constant, at 

 1-5238 grm. 



This residue (supposed to consist of only chloride of rubidium), when dissolved in 

 water, left a residue which was filtered off, ignited, and weighed. It weighed 3 mgrm. 

 The filtered solution was diluted to 201*465 grm., and divided into two portions. In one, 

 100*589 grm., the chlorine was determined with nitrate of silver ; weight of chloride of 

 silver obtained 0*9036 grm., corresponding to 0*22343 of chlorine or 0*4475 for the 

 whole. The other portion, 201*465 — 100*589 grm., was treated with sulphuretted hydro- 

 gen in the heat, which caused the formation of a small black precipitate. This precipitate 

 was filtered off, ignited, and weighed, and found to amount to 3*5 mgrm., or 7*0 for the 

 whole. The filtrate was evaporated to dryness, and the residue dried at 150° until 

 constant in weight, at 0*760 grm., or 1*5178 for the whole. But this probably included 

 a little sulphur from the excess of sulphuretted hydrogen, which had not been removed. 

 The platinum-free chloride gave 0*8964 grm. of chloride of silver, corresponding to 0*22165 

 of chlorine or 0*44267 for the whole. The 3 mgrm. of insoluble matter from the crude 

 chloride were unfortunately not examined qualitatively ; the ignited sulphuretted hydro- 

 gen precipitate consisted of metallic platinum. This platinum, no doubt, was present in 

 the fuse in the form of Pt0 2 + xK 2 0, produced, in spite of the hydrogen, at the expense of 



