94 



TABLE II. 



Time 



Weight of dish 

 -f water 



decrease 



Weight of dish 

 + gelatine 



i decrease 



2"d experiment (three dishes of water). 



time weight noi decrease 'weight n02 decrease weight n" 3 decrease 



24 hours 

 24 



81.129 

 80.868 

 80.601 



.261 

 .267 



64.399 

 64.041 

 63.709 



.358 

 .332 



45.888 

 45.591 

 45.291 



.297 

 .300 



temp. 22= 

 (room). 



We see from tliis that, in taking the experiment in this waj', a 

 dish of water decreases in weight 200 to 300 niG. in 2'4 hours, and 

 that consequently the experiments thus made with gelatine, do not 

 prove anything whatever. 



It is not quite easy to say where this water goes to. It might be 

 thought Ihat it serves to saturate the whole space of the desiccator 

 with vapour; but for tliis a much smaller quantity suffices, 1 L. 

 saturated watervapour of 22° only weighing 19 mG. Nor are 

 differences of temperature probable, because the changes we have 

 found always go in one direction, and because we cannot think 

 why the water in the middle of the desiccator should always be 

 warmer than the walls thereof. Besides the temperature in the room 

 was rather high ^), only varying within 0,5°, and so the dishes, 

 after being weighed, would sooner enter colder than warmer. 

 It was also controlled if a loss of weight occurred during the 

 weighing and the preparations for it ; by working quickly however, 

 this loss coidd easily be kept under 1 mG. The only explanations 

 left are, either the watervapour diffuses to the outside, passing 

 through the layer of grease which is between the desiccator and 

 the lid, or water is adsorbed at the great glass surface of the de- 

 siccator. The latter explanation will be most probable, as in smaller 



M Except in two series of table III, where the differences are equally great 

 all the same. 



