434 



PROFESSOR W. DITTMAR ON THE BEHAVIOUR OF THE 



Experiment II. — Substance taken = 1*1965 ; loss at 100° = 0*52535 grm. Weights 



of successive residues : — 



60 minutes at 100° 0*67115 



15 „ 220° 0*6710 



15 „ 250° 0*67125 



15 „ 320° 0*67105 



For the determination of the carbonic acid and of the lithia, a known weight of 

 crystals was decomposed by hydrochloric acid in a Classen apparatus, and the C0 2 

 absorbed in soda-lime and weighed. The residual chloride was converted into neutral 

 sulphate, and the latter weighed, to be calculated into Li 2 0. 



(2) (3) 



0*8809 0*9966 



8*25 mgrm. 9*25 mgrm. 



0*897 " 0*936 0*928 



1*1560 not done 1*2560 



34-527 ... 34*385 



Substance, . 

 C0 2 found, . 

 Percentage of C0 2 , 

 Sulphate obtained, 

 Percentage of Li 2 0, 



(1) 

 0*9135 



8*2 mgrm. 



From the means we have 



Lithia, Li 2 0, . 

 Carbonic acid, C0 2 , 

 Water volatile at 100°, 

 Other water and errors, 



Per cent. 

 34-460 

 0*920 

 43-864 

 20-756 



Multiples of Formula- Values. 



0*0186Li 2 CO 3 + (Li 2 + 1*023 H 2 0) + 2 '163 x H 2 

 of water volatile at 100° C. 



Considering that the number 1*023 in the bracket is burdened with a number of 

 observational errors, and that (by an error of judgment) all the components were not as 

 far as would have been possible determined in the same quantity of substance, we may 

 accept it as a sufficient approximation to unity, and conclude that lithia-crystals lose their 

 crystal-water at 100° and that the residual LiOH remains undecomposed up to 320° C. 



It is rather surprising to see a substance like LiOH lose its crystal- water completely 

 at so low a temperature as 100° C. Lithia obviously in this respect comes nearer to 

 baryta than to potash or soda, with which it is habitually grouped together. A similar 

 result was arrived at in the determination of the solubility in water at a series of tempera- 

 tures, on which I will now proceed to report. 



Experiments at 19°4. — 10 c.c. of boiled-out water were placed in a glass-stoppered 

 bottle of about 50 c.c. capacity, a presumably more than sufficient quantity of crystals was 

 added, the stopper put on and the bottle kept immersed in a water-bath, the temperature 

 of which was maintained at 19°*4 (the "20" of an ordinary thermometer) for three 

 hours. During the first hour the bottle was frequently agitated ; during the other two 

 hours the bottle was left undisturbed, to enable the undissolved part of the substance to 

 settle. A convenient quantity of the clear supernatant liquor was then drawn off with a 

 pipette, previously tared, along with a test-tube just wide enough to accommodate it, and 

 weighed (pipette and contents) in the test-tube. The solution was then promptly trans- 

 ferred to a Classen apparatus, the carbonic acid liberated, collected in soda-lime, and 



