Chemistry and Physics. 4.59 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. A Peculiarity of Platinum Amalgam. — When mercury is 

 shaken up with water, it is well known that the two liquids 

 separate as soon as the agitation is stopped. Moissan has 

 observed that it is otherwise when the mercury contains platinum 

 in solution. After a few seconds of agitation the platinum amal- 

 gam forms a semi-solid mass of buttery consistency with a vol- 

 ume about five times as great as that of the original amalgam. 

 The emulsion thus formed is so permanent that it does not appear 

 to have changed its volume after standing at rest for a year. It 

 resists the action of heat, for it may be heated to 100° without 

 apparently changing its volume, and without any disengagement 

 of gas. It resists the action of cold, and when an emulsion made 

 with water containing fuchsine was cooled to —80° and a section 

 was made of the frozen mass, this showed a cellular structure 

 under the microscope due to globules of water. When the 

 emulsion is subjected to a vacuum it diminishes in volume, a 

 little water separates, and bubbles of gas are given off. 



Amalgams of copper, silver, and gold do not produce such an 

 emulsion, but platinum amalgam forms the emulsion not only 

 with water, but with sulphuric acid, solutions of ammonia, ammo- 

 nium chloride, and sodium chloride ; with glycerine, acetone, 

 absolute alcohol, ether, essence of turpentine, carbon tetra- 

 chloride and chloroform. It appears to have no effect with dry 

 benzene. All the emulsions thus produced are stable. 



The emulsion may be made by shaking 2 CC of pure mercury 

 with 12 cc of distilled water to which has been added a few drops 

 of 1 per cent solution of platinic chloride. — Comptes Pendus, 

 cxliv, 593. h. l. w. 



2. The Explosion-Limits of Certain Gas Mixtures. — By 

 means of a special piece of apparatus, which will not be described 

 here, N. Tecxu has determined the lower and upper limits at 

 which mixtures of several combustible gases with air are explo- 

 sive. These results are given in the following table : 



Lower explosion- Upper explosion- 

 Kind of gas limit in per cents. limit in per cents. 



Hydrogen... 9-73-9-96 62'75-63-oS 



Illuminating gas 4-36-4-82 23-35-23-63 



Marsh gas 3-20-3-67 7-46-7-88 



Acetylene 1-53-1-77 57-95-5865 



The results show marked differences in the percentages re- 

 quired to form explosive mixtures, marsh gas showing the nar- 

 rowest range and acetylene the widest one. — Jour, prakt. Chem., 

 lxxv, 223. h. l. w. 



3. (A New Method of Forming Organic Compounds of Phos- 

 phorus.) — It has been found by Berthaud that when white 



