148 Prof. D. Mendeleeff. On the Weight of a Cubic [Dec. 5, 



tion only the data obtained by means of the large cylinder, especially 

 as in all instances relating to the weighings they are much more 

 reliable and symmetrical, that is to say, the changes of weight 

 follow uniformly with the changes of temperature. 



With the large cylinder (as with the small) Kupffer made many 

 series of alternate weighings in air and water. He first used ordi- 

 nary once distilled water, and afterwards water which was especially 

 prepared for him by the well-known chemists, Hess and Fritzsche. 

 According to all test proofs this water appeared to be pure,, and 

 before the experiment it was boiled to remove the dissolved air. 

 Only data given for pure water are of the greatest importance. 

 From the data obtained with the water first used we can only con- 

 clude that its density in relation to that of pure water appeared to 

 be 1*000128, if we judge from the corrected weighings of the large 

 cylinder. We expect therefore to find that the weight of a cubic 

 decimetre, using ordinary once distilled water, may give an increase 

 amounting to decigrams. 



The weight of the large cylinder in air was determined by thirty- 

 five weighings, distributed in six series, the mean results of which 

 are : 



Number 

 of 



weighings. 



The mean 

 observed weight 

 in arbitrary 

 units, A.* 



Readings 

 of 



barometer 

 at 0° in 

 inches. 



Corrected 

 tempera- 

 ture in 



degrees R. 



Psychro- 

 metrical 

 difference 

 in degrees 

 R. 



Kupffer, 

 vol. ii. 



10 



25560 -9621 A 



29-81 



12 -30° 





page 275 



5 



25561 0l7lf „ 



29-77 



13 -45 



3-17° 



„ 280 



5 



25560-8851 „ 



29-98 



12-30 



3-61 



„ 284 



5 



25560-6791 „ 



29-97 



12 -20 



2-80 



„ 289 



5 



25560-4155 „ 



30-45 



13-30 



3 00 



„ 293 



5 



25560-7482 „ 



29 -90 



13 -40 





„ 307 



The results being so remarkably close to one another, we are per- 

 mitted to take the mean: Weight in air, 255607884 A, H = 29*98 

 = 761*48 mm. ; h (pressure of aqueous vapour, humidity 61 per cent.) 

 = 8*26 mm. ; t = 12-825° ; ft. = 16-03° C. Hence we find e (weight 

 of litre of air) = 1*2205 grams, or the weight of a cubic inch of 



* For the weighings Kupffer used the working pound D with its verified sub- 

 divisions, and only at the end of his investigation, as shown later on, established 

 the relation of this pound to the standard Russian pound N ; the result being 

 A = 1 * 00000933 dolias of a Russian pound. 



f In the computat? on of the mean for this observation in Kupffer' s paper there 

 is a misprint or error; it is printed 2 lb., 74 zol., 35 -0171 dolias, but it should be 

 2 lb., 74 zol., 25 '0171 dolias = 25561 '0171 A. 



