OF ARTS AND SCIENCES. 



189 



It will be noticed that in experiments (23), (24), (26), and (27), the 

 corrected error in the weight of the insoluble chloride has a positive 

 value ranging from 0.0002-|- grm. to 0.0010-]- grm. with a mean of 

 0.00064- gi""^-; and that in experiments (25), (28), (29), (30), and 

 (31), the mean error is negative, amounting to less than 0.0001 — 

 grm., with a range from 0.0005 — grm. to 0.0007-)- grm. 



The point of difference between these two series of experiments is 

 the amount of lithium chloride introduced, only a tenth of that used in 

 the former being employed in the latter. It is plain that, when we 

 are dealing with the larger amount, a larger portion tends to remain 

 behind with the insoluble chloride ; and here again we meet, though to 

 a degree comparatively harmless, the inclination of lithium chloride 

 to yield chlorine and pass to the form of lithium hydrate. When the 

 lithium chloride is present in small amount, as in the latter group of 

 experiments, there can be little left undissolved ; and the spectroscope 

 confirms the evidence of the figures of analysis as to the perfectness of 

 the separation, by showing in such cases either no lithium at all or 

 merely fugitive traces. If a single precipitation is sufficient to effect 

 a satisfactory separation of the insoluble chlorides from small amounts 

 of lithium chloride, it is natural to suppoe that a repetition of the 

 precipitation would be beneficial in treating larger quantities of lithium 

 chloride. Experiments (32) to (37) illustrate the effect of a double 

 precipitation. The chlorides were brought to filtration as before, the 

 liquid was decanted as completely as possible, the precipitate washed 

 slightly by decantation and redissolved in a little water, and the 

 round of boiling, filtering, drying, and weighing carried to the 

 end as before, care being taken to repeat the treatment with a 

 drop of hydrochloric acid during the process of boiling. The two 

 portions of residual amyl alcohol were measured apart, as well as 

 the washings. 



