1889.] 



Zirconium and its Atomic Weight. 



83 



shows the highest proportion of chlorine would give the atomic 

 weight of zirconium as 92, which is undoubtedly too high, and, more- 

 over, it will be quite evident from these numbers that no trustworthy 

 determination was to be expected from this salt. 



The Tetrabromide. 



This salt was prepared by heating zirconia in an atmosphere of 

 bromine vapour, but proved no more promising in its behaviour than 

 the corresponding chlorine derivative. 



The Sulphate. 



Several methods of preparing the sulphate were tried, but ulti- 

 mately that originally used by Berzelius was adopted. Finely 

 powdered zirconia (air-dried) was heated with concentrated sulphuric 

 acid, and most of the excess of acid driven off at as low a temperature 

 as possible. In order to obtain the normal sulphate Berzelius drove 

 off the excess of sulphuric acid, and then heated for a quarter of an 

 hour, but never to redness ; Mats Weibull heated till constant at 300°, 

 a temperature manifestly too low. Cleve, in a private communication, 

 advised me to heat in a sulphur bath (442°). It seemed/however, 

 that in this instance, where the atomic weight depended on deter- 

 minations from the sulphate alone, and especially since this is a 

 general method applicable to several other elements, it was desirable 

 that the limits of temperature within which the normal sulphate was 

 stable ought to be ascertained. This was done in the case of a 

 number of sulphates (Bi, Mg, Zn, Di), and the details of the investi- 

 gation have already appeared (' Chem. Soc. Journ.,' vol. 51, p. 676). 



The salt containing excess of sulphuric acid was heated in a bath, 

 described in that communication, which could be easily kept within 

 5°, and at any temperature up to 500°. The boat containing the salt 

 was weighed from time to time until it became nearly constant. The 

 salt was then finely powdered, and the heating continued in periods 

 of about four hours, until no further diminution of weight occurred, 

 showing that the free sulphuric acid had been got rid of. The tem- 

 perature of the bath was now raised by intervals of about 10°, and 

 the heating continued for several hours at each limit, weighings being 

 made after each increment until a point was arrived at at which loss 

 of weight was again observed. This indicated that the temperature 

 had been attained at which the normal salt began to undergo decom- 

 position. We have then the limits of temperature within which the 

 normal sulphate is stable. Several series of determinations were 

 made, and one of these is given to show the character of the values 

 obtained. 



G 2 



