TRANSACTIONS OF SECTION B. 



631 



4. The Atomic Latent Heats of Fusion of the Metals considered from the 

 Kinetic Standpoint. By Holland Crojipton. 



According to the kinetic theory, if a fluid is composed of monatomic molecules, 

 the iiuetic energy given to the particles of the fluid on heating, if no external 

 work is done, is equivalent to 2-9G x T calories for the gram-molecule. If it is 

 assumed that in the solidification of such a fluid the process consists mainly m 

 bringing the molecules (in this case atoms) to rest, or in largely restricting their 

 motion, kinetic energy approximately equivalent in amount to 2-96 x T calories 

 should he lost by the gram-molecule. Hence in the above case the molecular 

 (atomic) latent heat of fusion Ar should approximate to 2-96 x T calories, or 



As a matter of fact, the values of Ar/T in the case of fourteen diflerent metals, 

 presumably of monatomic structure, vary between 1-82 for potassium and 3-05 for 

 tin, the average value being 2-4. Up to the present only two cases have been met 

 with among the metals in which the determined values of r do not bring Ar/1 

 within these limits, these being gallium and bismuth, for which the values of 

 Ar/T are 4-67 and 4-82 respectively. 



5. The Influence of Small Quantities of Water in hrinying about Chemical 

 Reaction between Salts. By Edgar Philip Perman, B.Sc. 



Many experimenters have investigated the influence of traces of moisture in 

 reactions between gases, but so far as I am aware no one has hitherto made similar 

 experiments with solids. 



The substances chosen for experiment were salts of lead or mercury, and salts 

 of potassium, usually the iodide, which would show the occurrence and progress of 

 a reaction by a colour change. 



a. Experiments iiith Lead Chloride and Potassium Jot^tJ^.— Equivalent quanti- 

 ties of the two salts were dried over strong sulphuric acid in a suitable apparatus, 

 and then mixed; it was found that after forty-eight hours' drying no visible change 

 took place on mixing the salts, but on keeping the mixture for a week (in a sealed 

 flask) a faint yellow colour appeared, which gradually deepened, until after some 

 months it became a bright yellow. 



Attempts were made to discover bow much water was necessary m order to 

 make the reaction immediately visible ; the results were not very concordant, but 

 indicated about -5 mg. as the amount necessary in the conditions of the experi- 

 ment, viz. two grams of potassium iodide and an equivalent quantity of lead 

 chloride were mixed in a glass flask of about 100 c.c. capacity. 



b. Experiments with other Lead Salts and Potassium Iodide. — Lead formate 

 and lead nitrate were found to act in a similar way to the chloride. 



Lead sulphate reacts much more slowly, although exposed to the air, while 

 the carbonate and the oxide react very slowly indeed. 



c. Experiments with Mercuric Chloride and Potassium Iodide.— Severn ic 

 chloride and potassium iodide treated in exactly the same way as already described 

 gave a strong red coloration on mixing; the same result was obtained when 

 commercial phosphoric anhydride was used as a drying agent. By drying with 

 specially prepared phosphoric anhydride, however, the mixture obtained has been 

 kept for some months without change. 



d. Other E.rperiments with Mercuric Salts.— Mevcunc cyanide showed no 

 reaction with potassium iodide. 



Mercuric chloride and potassium chromate reacted very slowly, although exposed 

 to the air. 



Discussion of Results.— There is no reason for thinking that_tlies« reactions 

 take place in any way essentially different from similar reactions in solution, and 

 I believe that the only difference is the extreme slowness of the reaction. It is 



