84 



Dr. G. H. Bailey. 



[May 9, 



Grams. 



Weighing tube and boat 20*64962 



„ „ and salt 22-9095 



After heating 6 honrs at 300° 22*9045 



7 „ 330 22 9015 



4 „ 350 22-9002 



4 „ 365 22-90012 



5 „ 380 22-90025 



4 „ 390 22-90020 



4 „ 410 22-89820 



The above numbers have not had applied to them the small correc- 

 tions for variations of barometer and thermometer, and no importance 

 need be attached to the differences of one or two tenths of a milli- 

 gramme between 350° and 400°. 



It appears, therefore, from these experiments that zirconium sul- 

 phate is stable up to 400°, and that the excess of sulphuric acid is 

 driven off completely at 350°. If, therefore, a mixture of the salt and 

 the free acid, prepared as above, be heated at any temperature between 

 350° and 400° till constant, we shall obtain the normal sulphate. The 

 temperature of the sulphur bath would be too high, and of course at 

 dull redness decomposition would set in. 



The Atomic Weight of Zirconium. 



After what has been said it may appear that the previous determi- 

 nations of atomic weight from the sulphate would be too high rather 

 than too low, since there can be little doubt that Berzelius heated the 

 salt above 400°. It does not follow, however, that by heating it for 

 a short time at a moderately high temperature more than a small 

 fraction of the salt would be brought under conditions favourable to 

 decomposition, nor even would the temperature of the mass be such 

 that the whole of the free sulphuric acid would be got rid of. And 

 the fact that on repeating such a treatment no variation in weight 

 occurred, would be no guarantee that the salt was normal zirconium 

 sulphate. My own experiments show that to get rid of the excess of 

 acid requires prolonged heating, and at the same time renewal of the 

 atmosphere in the vessel containing the sulphate. Apropos of this, 

 Berzelius's precaution to introduce into the crucible in the last stage 

 of the ignition of the sulphate a little ammonium carbonate is a very 

 necessary one, as it displaces often 2 or 3 milligrams of sulphuric acid, 

 which otherwise seems to remain in the crucible time after time and 

 fix itself in the zirconia, when the crucible begins to cool. Further- 

 more, whatever previous experience may have been (for no special 

 precaution is mentioned in any case), I have found it most difficult to 

 ignite zirconium sulphate without loss; the decomposition occurs 



