414 



Mr. W. Crookes. 



[June 18, 



be distinguished from the intermixture of the liquefied solid with the 

 water. Both these acts must be attended by heat-absorption. The 

 dilution of watery solutions has been shown, especially by the 

 researches of Thomsen, to be attended very generally by absorption 

 of heat, notwithstanding that in most cases it is accompanied by con- 

 traction of volume, a process which must have an opposite effect. 



In the solution of many anhydrous and even hydrated salts, we 

 must believe, from the very energetic thermal change observed, that 

 the salt enters into chemical union with a portion of the liquid. The 

 extent to which this combination occurs will be greatly influenced by 

 the temperature at which the experiment is made, and at sufficiently 

 elevated temperatures it must be believed fco be entirely annulled, 

 whilst on the other hand, as the temperature is raised, chemical 

 action, resulting in double decomposition between the water and con- 

 stituents of the salt, becomes apparent. This action, which is mani- 

 fested in the case of the salts of the heavy metals by the production 

 of insoluble oxides, hydroxides, or basic salts, cannot be supposed to 

 be altogether without effect in the case of the salts of the alkali 

 metals such as I have been examining, and I incline strongly to the 

 belief that a part of the difference which I have pointed out between 

 the observed heat of solution and the same calculated according to 

 Person's formula, is due to this decomposing action of the water. 



It is manifest that no theory of solution can be accepted which does 

 not take cognisance of all these facts. 



In conclusion, I desire to acknowledge the intelligent assistance I 

 have received in the conduct of these experiments from Mr. Harold 

 P. White. 



V. "On Radiant Matter Spectroscopy. Part II. Samarium." 

 By William Crookes, F.R.S. Received May 21, 1885. 



(Abstract.) 



In the concluding sentence of the Bakerian Lecture which I had the 

 honour to deliver before the Royal Society, May 31st, 1883, I said that 

 the new method of Radiant Matter Spectroscopy there described had 

 not only given me spectrum indications of the presence of yttrium as 

 an almost invariable, though very minute, constituent of a large 

 number of minerals, but had likewise revealed signs of another 

 spectrum-yielding element. I stated that I had repeatedly seen 

 indications of another very beautiful spectrum characterised by a 

 strong red and a double orange band. 



