1825.J Scientific Notices — Chemistry. 389 



Article X. 



SCIENTIFIC NOTICES. 



Chemistry. 

 1 . Cold produced by the Combination of Metals. 



The elevation of temperature and even brilliant ignition which 

 take place at the instant of the combination of certain metals, 

 as of potassium or sodium with mercury, of tin or zinc with 

 platinum, &c. have been long familiarly known ; but chemists 

 were not, we believe, acquainted with the existence of any 

 analogous instances, in which the combination of metals is 

 followed by the production of cold. Sir H. Davy, indeed, 

 ascertained that the sohd amalgams of bismuth and of lead 

 hecome Jiuid upon being mixed ; but he does not appear to have 

 examined whether or not any depression of temperature results 

 from this sudden liquefaction. Some curious examples of this 

 latter description have been lately noticed by Dbbereiner. 



According to him, the fusible metal is a compound of 1 atom 

 of lead (=lU3-o), 1 atom of tin (= 59), and 2 atoms of bismuth 

 (=2 +71); or it consists of 1 atom of the atomic combination 

 of bismuth and lead, united to 1 atom of the atomic combina- 

 tion of bismuth and tin (Bi Pb + Bi Sn) ; and it becomes fluid 

 when exposed to a temperature of 210°. The melting points of 

 these alloys of bismuth and lead and of bismuth and tin in a 

 separate state, are respectively between 325° and 335°, and 

 between 268° and 280°. If 118 grains of Hlings of tin, 207 

 grains of filings of lead, and 284 grains of pulverised bismuth 

 (the constitutents of fusible metal), be incorporated in a dish of 

 calendered paper with 1616 grains of mercury, the temperature 

 instantly sinks from 65° to 14°. He is of opinion that it Would 

 even fall so low as the freezing point of mercury, were this 

 experiment performed in temperatures somewhat under 32°. 



In like manner, when 816 grains of the amalgam of lead 

 (composed of 404 mercury + 412 lead = Pb Hg), were mixed, 

 in a temperature of 68° with 688 grains of the amalgam of 

 bismuth (composed of 404 mercury + 284 bismuth = Bi Hg), 

 the temperature suddenly fell to 3U°, and by the addition of 808 

 grains of mercury (also at 68°), it became so low as 17°: the 

 total depression amounting to no less than 51 degrees. — 

 (Schweigger's Neues Journal der Cheniie und Physik, xii. 182.) 



Nothing can be a more decisive proof that metallic alloys are 

 true chemical combinations, than the foregoing experiments oi" 

 Dobereiner; and it is to be regretted, therefore, that our 



