HYDRATES AND CARBONATES OF THE ALKALI-METALS, ETC. 449 



raised so as to bring the carbonic acid within the porcelain tube up to the desired 

 tension, which was maintained as far as practicable by occasional readjustment of the 

 height of the reservoir. 



Counting from the time when the tube had come up to the full heat afforded by the 

 furnace, the experiments at to 2 inches over-pressure were continued for about one hour; 

 in the high-pressure experiments (at 15 or 30 inches over-pressure) the initial pressure (of 

 atmosphere + 2 inches) was kept up for about one hour, and the subsequent high pressure 

 for another half hour. At the end of an experiment, after the gas flames had been turned 

 off, the high pressure was always maintained until the temperature of the tube had sunk 

 so far that the carbonate inside could safely be assumed to have frozen. 



In now proceeding to give an account of the individual experiments, I will take 

 these up in what I conceive to be the most convenient order for the reader; the reference 

 marks give the order in which they were made. 



Experiments Q. — A quantity of carbonate of lithia was placed in the gas-crucible and 

 in it kept for 1 hour at a temperature just sufficient to fuse it, but no more, while a 

 current of carbonic acid of ordinary pressure was passing through the crucible. This 

 operation was carried out three times ; the three products were powdered roughly, mixed 

 together, and divided into four parts, of which three were weighed out at once along 

 with their respective preparation tubes, to be analysed for carbonic acid. The fourth 

 quantity was kept in reserve for emergencies. As one of the three analyses gave an 

 incomprehensible result, the fourth was broken into for an additional determination of 

 carbonic acid. The results were as follows : — 





(1) 



(2) 



(3) 



(4) 



Substance, 



5-3387 



5-6930 



5-9016 



2-3752 



Carbonic acid, 



3-1760 



3-3847 



34793 



1-4125 



Percentage of C0 2 , . 



59-490 



59-454 



58-955 



59-465 



Two portions of (4), each equal to about 1'8 grm., were analysed exactly with chloride 

 of barium. Found in one sample 0*063 percent, of Li 2 ; in the other, 0*049 and 0*056. 

 Omitting 0*049, which was obtained by a titration done on a very small scale, we have 

 0'060 for the percentage of free Lithia. Of the four carbonic-acid determinations 

 that in (3) was rejected as being in all probability infected with an unobserved grave 

 error; the mean of the other three is 59*470; hence so much C0 2 is contained in 

 100 — 0*060 = 99*94 parts of carbonate proper; hence the latter contains 59*506 

 per cent, of carbonic acid. 



Experiment E. — A quantity of the carbonate was dried in a current of carbonic 

 acid at 250°, at ordinary pressure. 4*9432 grm. gave 2*9500 grm. of C0 2 , or 59*678 

 per cent. 



Experiments A, B, and C were made with a supply of fused carbonate produced 

 under carbonic acid of 3 1 *8 inches pressure in instalments. 



The analyses gave the following results : — 



