2818.] Prof. Munche on the Boiling Point of Fluids. 131 



The Editors have subjoined an account of Prof. Munche's 

 experiments, which are referred to by M. Gay-Lussac in the 

 above paper, and also an extract, on the same subject, from 

 M. Biot's Traite de Physique. 



On the Fixedness of the Boiling Point in Thermometers. By 

 Professor Munche, of Heidelberg.* 



It had been announced by M. Gay-Lussac, that water boils 

 in metallic vessels at a temperature of 2*34 Fahr. (1-3 cent.) 

 lower than in glass vessels ; and M. Biot has since confirmed 

 the observation ; but the cause of so remarkable a fact has not 

 been yet ascertained or even examined. M. Munche, in con- 

 junction with M. Gmelin, undertook to repeat the experiments 

 and to endeavour to give some explanation of the facts. A 

 number of vessels of the same form were accordingly prepared, 

 three inches high and 1-3 inch in diameter, but of different 

 materials. Four of them, one of thick leather, another of beech 

 wood, a third of ivory, and a fourth of 12 folds of thin paper, 

 could not be made use of, because they were not sufficiently 

 good conductors of heat to enable the water to boil. Those that 

 were employed were of copper, tinned iron, tin, lead, and marble ; 

 they had also a goblet of silver and one of platina, the first *3 

 line thick ; the second, - 2 only ; also a vessel of varnished delft 

 ware, P6 inch in diameter, two cups in the form of goblets, 

 one of porcelain and the other of Delft ware, two inches in. 

 diameter, and lastly three medicine phials, of 1-|- in diameter, 

 one of white, the other two of green glass. The water in these 

 different vessels was kept as nearly as possible at the same 

 temperature, by placing them, in the same sand bath. The 

 following are some of the principal results that were obtained. 



1 . The heat of boiling water may be increased by the quick- 

 ness of the fire, so that the thermometer may be raised more 

 than one degree of Fahr above the boiling point on the scale. 

 2. When the bulb of the thermometer touches the bottom of the 

 vessel, particularly when it is inserted between the cone which 

 projects inwards and the sides of the vessel, the thermometer 

 rises still higher, as much as 1*8 Fahr. 3. The heat of the water 

 is diminished, when sand is thrown into it, by some tenths of a 

 degree ; a small quantity of copper filings, part of which swam 

 on the water, whilst the remainder fell to the bottom, produced 

 no effect. 



The following table contains the actual temperatures which the 

 water exhibited in the different vessels when in a state of ebulli- 

 tion, above or below the degree marked on the scale. 



• Abridged from Bibliotheque Universelle, vii. 101. (Feb. 1818) j and Journal 

 de Phys. lxixvi. 243. (March, 1818.) 



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