130 Chronicles of Science. [Jan., 



acid found in some of the same portion of breath by chemical means. 

 The accordance is very close. The fact revealed by the numerous 

 tables which the author has given in his paper,* leaves no doubt that 

 this method is a more delicate test for the presence of carbonic acid, 

 than the present chemical means. As such it will be of service in 

 many cases where chemical analysis would fail. If a simple and ready 

 means of making a physical analysis of breath can be devised, this 

 new method will undoubtedly be most useful in hospitals and else- 

 where. 



Electricity. — We have scarcely anything to chronicle this quarter 

 in electrical science. M. Eaoult has published some researches into 

 the Thermal Phenomena of Voltameters, and measures of the quantities 

 of heat absorbed in electro-chemical decompositions, f His experi- 

 ments, relating to sulphate of copper and acidulated water, lead to the 

 conclusion that a voltameter introduced into the current of a battery, 

 weakens the electro-motive force, and thus destroys in the complete 

 current a quantity of heat which is always greater than what is re- 

 quired for the decomposition effected. The excess varies according 

 to circmnstances ; but in every case a secondary action takes place at 

 the electrodes, whereby a quantity of heat is imparted to the voltameter 

 equal to the excess of heat destroyed, and finally the sum of the vari- 

 ous calorific effects of the voltameter is equal to the heat absorbed by 

 the decomposition which goes on within it. 



A valuable process for coating metals with firmly adherent and 

 bright layers of other metals, has been communicated by M. Weil, to 

 the Academy of Sciences. J The method consists in dipping the metal 

 to be coated in a saline solution of the metal to^be deposited, rendered 

 distinctly alkaline with potash or soda, and mixed with some organic 

 matter, such as tartaric acid or glycerine. At the same time it is 

 necessary, in some cases, to set up a weak voltaic current, by keeping 

 a piece of zinc or lead in contact with the metal. In this way the 

 author obtains a firm layer of copper on iron and steel, and procures 

 various and beautiful effects, according to the thickness of the copper 

 deposited. Silver, nickel, and other metals, can be applied in the same 

 way. The process, it will be seen, is susceptible of numerous applica- 

 tions. A curious fact mentioned is, that a clean surface of copper 

 may be coated with zinc, by placing the two metals in contact in a 

 solution of caustic, potash, or soda. In the cold the deposit of zinc 

 takes place slowly, but at 100° C. it is effected rapidly. 



* 'Phil. Mag.,' August, 1864. 



f ' Phil. Mag.,' Dec. 1864. Supplementary number. 



I 'Comptes Rendus,' Nov. 7, 1864. 



