152 



CHEMISTRY. (PHYSICS.) 



can be produced on employing a mixture of ice 

 and the salt as a freezing mixture. The pro- 

 cess is an example of eutexia. Eutectic salt 

 alloys, or fused mixtures of salts, closely re- 

 semble cryohydrates in behavior. If they are 

 present in any other proportion than the eutec- 

 tic, the thermomete^ on cooling them, will fall 

 steadily till that salt which is in excess of the 

 proportion required for a eutectic mixture be- 

 gins to separate. When this is removed, and 

 the process is continued, the whole will be 

 found to solidify at a point which is fixed. 



Raoult has studied the effect produced upon 

 the point of solidification of a solvent by dis- 

 solving solid, liquid, or gaseous substances in 

 it, and has reached the following conclusions : 

 That all bodies, whether solid, liquid, or gas- 

 eous, when dissolved in a definite compound 

 liquid capable of solidifying, lower the point 

 of congelation ; that there is for each solvent a 

 maximum molecular depression (or depression 

 corresponding to the solution of one molecule 

 of the dissolved substance in one hundred 

 grammes of the solvent) of the freezing-point ; 

 and that with all solvents the molecular de- 

 pression of the freezing-point, due to the dif- 

 ferent substances dissolved, approximates to 

 two mean values, differing with the character 

 of the solvent, one of which is double the 

 other. A number of special experiments in 

 the application of the last principle seemed to 

 justify the generalization that, for a constant 

 weight of a given solvent, all physical molecules 

 of whatever nature produce the same depres- 

 sion of the freezing-point. When the bodies 

 dissolved are completely disaggregated, as for 

 example when they are in a state of vapor, so 

 that each physical molecule contains only a 

 single chemical molecule, the molecular de- 

 pression is at a maximum, and is the same for all 

 bodies. When the chemical molecules are united 

 in pairs to form the physical molecule, the de- 

 pression has only one half its former value, 

 since the double molecule produce? no more 

 etfect than the single one. If the maximum 

 molecular depression be divided by the mo- 

 lecular weight of the solvent, the quotient ex- 

 presses the depression produced when one 

 molecule of the substance is dissolved in one 

 hundred molecules of the solvent. In subse- 

 quent papers, Raoult considers the application 

 of this law to the study of the distribution of 

 acids and bases in solution, and of the freezing- 

 point of acid and alkaline solutions. 



Dr. W. W. J. Nicol, of the Committee on So- 

 lution, of the British Association, reports: 1. 

 That the results of a series of experiments show 

 the molecular volume of a salt in dilute solu- 

 tion to be a quantity composed of two con- 

 stants ; one for the metal and the other for the 

 salt radical. Hence the same volume change 

 is produced by replacement of one metal or 

 salt radical by another metal or salt radical. 

 Water of crystallization is not to be distin- 

 guished from the solvent water, but the water 

 of constitution possesses a volume different 



from that of the rest of the water. These re- 

 sults show the existence in solution of the an- 

 hydrous salt in contradistinction to the view 

 that a hydrate, definite or indefinite, is formed 

 in solution. 2. Saturation is reached when the 

 further addition of salt would produce diminu- 

 tion of the mean molecular volume of the mole- 

 cules already present. 3. The so-called super- 

 saturated solutions are simply saturated or non- 

 saturated solutions of the anhydrous salts, the 

 only truly supersaturated solutions being those 

 resulting from the fact that, when a hot solu- 

 tion is cooled, a finite time is required for the 

 excess of salt to crystallize out. 



M. L. Cailletet approves of liquid ethylene 

 as affording the best agency for effecting the 

 liquefaction of oxygen. When boiling in the 

 free air it gives a degree of cold such that oxy- 

 gen if compressed and cooled to the same tem- 

 perature presents, on diminishing the press- 

 ure, a tumultuous ebullition which lasts for an 

 appreciable time. On quickening the evapora- 

 tion by means of the pneumatic machine, the 

 temperature is lowered so far as to bring the 

 oxygen to a liquid state. The author had tried 

 to obviate the necessity of working with ethy- 

 lene in a vacuum by using liquid formene, but 

 he found that ethylene was so easy to prepare 

 and manage as to be on the whole preferable. 

 He then sought a method for obtaining, by 

 means of ethylene boiling in open vessels, a re- 

 duction of temperature sufficient for the com- 

 plete liquefaction of oxygen. For this purpose 

 he now employs a simple process consisting 

 of intensifying the evaporation of the ethylene 

 by forcing into it a current of air, or of hydro- 

 gen cooled to an exceedingly low temperature, 

 tinder these circumstances the temperature 

 may be reduced to quite below the critical 

 point of oxygen, and the gas most distinctly 

 liquefied. 



Prof. Dewar, in reporting on his experiments 

 with liquefied oxygen, statesthatat 130liquid 

 oxygen loses the active characters possessed by 

 the element in the gaseous state. It is without 

 action on phosphorus, sodium, potassium, solid 

 sulphureted hydrogen, and solid hydriodic acid. 

 Other substances appear to undergo similar 

 changes at very low temperatures. Thus liquid 

 ethylene and solid bromine may be brought in 

 contact without any action taking place, where- 

 as gaseous ethylene and liquid bromine unite 

 directly at the ordinary temperatures. Haute- 

 feuille and Chapuis, by subjecting a mixture of 

 carbonic anhydride and ozone to great pressure, 

 obtained a blue liquid, the color of which is 

 due to the ozone. If ozonized air be passed 

 into carbon disulphide at 100, the liquid 

 assumes a blue color, which disappears if the 

 temperature be allowed to rise, and at a cer- 

 tain point a decomposition, resulting in the 

 production of sulphur, takes place. The best 

 solvent for ozone is a mixture of silicon tetra- 

 fluoride and Russian petroleum. These solu- 

 tions of ozone are without action on metallic 

 mercury or silver. 



