102 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



after the agitation. This experiment was made long since 

 by Duprez, but without any explanation. It is impossible to 

 attribute the effervescence to the air introduced by the agi- 

 tation, since the alcohol and ether alone, or water alone, give 

 no marked result in this respect. The experiment succeeds 

 equally with benzine, sulphide of carbon, creosote, turpentine, 

 olive-oil, lavender, etc. It is only necessary to shake the dis- 

 tilled water, after having introduced a glass rod containing 

 a slight quantity of any fatty body whatever, in order to per- 

 ceive a distinct disengagement of small bubbles of gas. 

 Bull. Acad. Eoyale de Belgique, 1872, in., 223. 



VALSON S LAW. 



According to Les Mondes, Professor Valson, of Montpellier, 

 has discovered an important physical law, expressed in the 

 following terms : For all normal solutions that is to say, 

 containing each one equivalent of nitrous salt, estimated in 

 grams, and dissolved in a fixed quantity of water equal to 

 one liter the product of the density by the capillary height 

 remains sensibly constant. 3 B,Jan. 18, 1872, 91. 



SEXSIBILITY OF IRIDIUM, ETC., TO MERCURIAL VAPOR. 



Professor Merget, in a communication to the Academy of 

 Sciences of Paris, states that when solutions of iridium, plati- 

 num, and other metals in nitro-muriatic acid are brought into 

 relations with metallic mercury, their sensibility is so great 

 that if a paper be impregnated with such a solution and ex- 

 posed to the vapor of mercury, in however small a quantity, 

 it becomes colored black, forming, as it were, an actual in- 

 delible ink. From his experiments the author infers that 

 mercury evaporates with a velocity of 180 meters per second, 

 and reaches to a height of 1700 meters. A practical test of 

 these experiments of Professor Merget shows that by means 

 of iridium paper so prepared, the presence of mercury can be 

 ascertained in the atmosphere of all workshops where this 

 metal is employed, especially in looking-glass manufactories. 

 It also shows that the clothes, hair, etc., of a workman who 

 has spent an hour in such an establishment become entirely 

 impregnated with mercury, and that it is only necessary to 

 bring his hand near paper prepared with iridium in order to 

 have it instantly outlined in black. It is not at all impossi- 



