132 M. Biot on the Boiling Point of Fluids. [August^ 



Substance of the 

 vessels. 



Silver , 



Platina 



Copper 



Tinned iron. . . 

 Marble 



XjGcICi • • • « • • 



Tin.... 



Porcelain .... 

 White glass. . . 

 Green glass. . . 



Ditto 



Delft ware . . . 



Common earth 



enware 



Temperature. 



The thermometer When the thermometer was half an inch 

 touching the bottom. below the surface of the water. 



- 0-225 Fahr. 



- 0-226 

 + 0-9 

 + 1-24 

 + 0-1 

 + 0-45 

 + 0-7 

 + 0-1 

 + 0-7 

 + 1-8 

 + 0-7 

 + 1-8 



+ 1-8 



-0-45 Fahr. 



- 1-125 

 + 0-225 

 -0-34 

 -0-34 



- 0-225 



- 0-225 

 -0-1 



0-0 

 + 1-35 



0-0 

 + 0-7 



+ 0-45 



The inside of the metallic vessels, although they were not very 

 highly polished, were so much so as to have a degree of 

 metallic lustre. The silver goblet had on one side a black spot 

 owing to the metal having been a little acted upon in that 

 part. As soon as the bulb of the thermometer touched this 

 spot, it rose more than a degree of Fahr. and upon touching the 

 bottom, it fell to the point marked in the table ; this curious 

 observation has been frequently repeated, and always with the 

 same results. 



The author explains the results of his experiments upon the 

 principle that the heat passes through the bottom of the vessels, 

 is united to the water, and forms elastic vapour ; but the vapour 

 thus formed is ,a conductor of heat; and besides the caloric 

 necessary for its formation, contains also a certain quantity of the 

 same cajoric which is capable of affecting the thermometer. The 

 proportion of the two quantities of heat depends upon the nature 

 of the substance in which the water is boiled, and also upon the 

 state of the two surfaces, internal and external, so that the 

 different quality, as well of the substance as of either of the 

 surfaces, may affect the results, but not so as materially to affect 

 the accuracy of the thermometer. 



Extract from M. Biot. 



" There is also some variation in the boiling point according 

 to the nature of the vessels which we employ, and according to 

 that of the substances which are mixed with the water, even 

 when it cannot dissolve them. For this observation we are 



