474 SEC. 13. CHEMISTRY. 



mometer was tested recently by Mr. Baxendell, who found that it had not 

 altered since the instrument was graduated. 



Another (No. 4) is of the same kind, and bears the date 1823. 



No. 5 js a third mercurial thermometer with long stem and wooden scale. 



No. 6 is an alcohol thermometer with wooden scale. 



No. 7 a registering maximum and minimum thermometer employed by 

 Dalton ; maker's name J. Renchetti, 29, Balloon Street, Manchester. 



II. Apparatus constructed and used by Dalton in his Researches. 



(1) " On the constitution of mixed gases," (2) " On the force of steam or 

 " vapour from water or other liquids at different temperatures both in a Torri- 

 " cellian vacuum and in air," (3) on evaporation, and (4) " On the expansion 

 " of gases by heat."* 



No. 8 is an apparatus used for the determination of the tension of volatile 

 liquids at low temperatures ; it consists of a siphon tube, at the upper end of 

 which is a scale in inches in Dalton's handwriting. He describes it thus : 



" I took a barometer tube 45 inches in length, and having sealed it her- 

 metically at one end, bent it into a siphon shape, making the legs parallel, the 

 end that was closed being 9 inches long, the other 36 inches. I then con- 

 veyed two or three drops of ether to the end of the closed leg, and filled the 

 rest of the tube with mercury, except about 10 inches at the open end. This 

 done, I immersed the whole of the short leg containing the ether into a tall 

 glass containing hot water." 



No. 9 is a smaller tube containing another liquid, also having a graduated 

 scale written on paper and attached to the tube. 



Nos. 10, 11, 12, 13, 14, are tubes used by Dalton for measuring the tension 

 of vapour from water and other liquids at higher temperatures than their 

 boiling points, both in a vacuum and air. 



No. 15 is a tube used by Dalton for measuring the tension of the vapour 

 of bisulphide of carbon, labelled " Sulphuret carb.," with a paper scale in 

 Dalton's handwriting, and a cork showing that the upper portion of the tube 

 containing the bisulphide of carbon could be heated in a water bath to various 

 temperatures. 



No. 16 is a manometer tube, fixed into a board, divided and numbered by 

 Dalton. 



No. 17 is an apparatus used by Dalton for the determination of the tension 

 of the vapour of ether, and is interesting as being the instrument by means of 

 which Dalton arrived at one of his most important experimental laws. It is 

 described as follows (p. 564.) : 



"The ether I used boiled in the open air at 102. I filled a barometer 

 tube with mercury moistened by agitation in ether ; after a few minutes a 

 portion of the ether rose to the top of the mercurial column, and the height of 

 the column became stationary. When the whole had acquired the tempera- 

 ture of the room (62) the mercury stood at 17*00 inches, the barometer 

 being at the same time 29'75 inches. Hence the force of the vapour from 

 ether at 62 is equal to 12'74 of aqueous vapour at 172 temperature, which 

 are 40 from the respective boiling points of the liquids." 



This is generally known as Dalton's law of tensions, since shown by "Reg- 

 nault not to be rigorously true. 



No. 18 is a wet and dry bulb mercurial thermometer made by H.H. Watson, 

 ofBolton. 



* Experimental essays on the above subjects, by John Dalton, read October 2nd, 16th, 

 and 30th, 1801, and published in the 1st series, vol. 5, part 2, of the Memoirs of the Lite- 

 rary and Philosophical Society of Manchester. 



