M. 



N. 



P. 



59-95 



44-7 



59-73 inch. 



4-3870 



4-2880 



4-373 grm. 



2-6174 



2-5558 



2-6027 grm. 



59-663 



59-604 



59-518 



HYDRATES AND CARBONATES OF THE ALKALI-METALS, ETC. 451 



Pressure of C0 2 in tube, . 

 Substance for analysis, 

 C0 2 obtained, .... 

 Percentage of C0 2 , . 



Experiment O. — Carbonate of lithium fused for one hour in a porcelain tube under 

 carbonic acid of 29*5 + 2*2 = 31 '7 inches pressure. 4*8665 grm. of the product gave 

 2*9005 grm. of carbonic acid, or 59*601 per cent. 



The products M, N, 0, and P were compact homogeneous glassy fuses. 



We will now proceed to discuss these results, and first of all notice that, in the 

 porcelain tube experiments, only one, namely, Experiment F, which was made at 

 29*2 inches of carbonic-acid pressure, gave a product containing free lithia ; in all the 

 rest, made at pressures from 31*7 inches upwards, neutral (or perhaps quasi acid) products 

 were obtained. This shows that at the temperature which prevailed in the porcelain 

 tube in these experiments the dissociation-tension of carbonate of lithia lies between 

 29 *2 and 31*7 inches of mercury. Another glance at the numbers shows that the carbonic 

 acid taken up by the heated carbonate did not increase with the pressure of the carbonic- 

 acid atmosphere under which it is prepared. The numbers, if taken as they stand, 

 would rather point the other way. The mean of the percentages of carbonic acid found 

 for products A, C, G- and O, for which the pressure varied from 317 to 30*2, is 59*646, 

 while the mean of the high-pressure experiments M, N and P is 59*595. 



We will now proceed to view the analyses as so many determinations of the value 

 Li 2 0, and begin with the case of Q, because these analyses afford an upper limit for the 

 constant. A substance proved to contain free lithia gave in three well-agreeing analyses, 

 (1), (2) and (4), 59*470 per cent, of carbonic acid; hence the weight of lithia which in 

 it was associated with C0 2 = 44 parts of carbonic acid, amounts to 44 x 40*53-^59*470 = 

 29*987 parts of lithia, and this, if the substance were normal carbonate, would be the 

 value of Li 2 0, whence we should have Li = 6*993. But the substance analysed, 

 according to our analysis by chloride of barium, contained 0*060 per cent, of free lithia. 

 Taking this number to be correct, we have Li 2 0= 13*943, whence Li = 6*971. This 

 latter number must of course be taken for what it is worth, but the value calculated 

 from the uncorrected carbonic-acid determinations proves that Li must be less than 6*993. 



We will now pass to the analysis of product E, which ought to afford a lower limit 

 for the true value Li, because the substance may have contained more, but cannot have 

 contained less, than the proportion of carbonic acid corresponding to normal carbonate. 

 From the percentage of carbonic acid found (59*678) we calculate Li 2 = 29*729 and 

 Li = 6*865. But this calculation is based upon only one analysis. 



The following table summarises the results of all the porcelain tube experiments, 

 excepting F, which of course is out of court. The second column gives the pressure of 

 the carbonic-acid atmosphere under which the respective carbonate was produced. 



