97 



So we again found a decrease of weight in all cases, be it less 

 than with the experiments made before. As the amonnts are so mnch 

 smaller here, another circumstance, except the one of adsorption at 

 the glass walls, must be taken into consideration, which, as we have 

 found with the apparatus presendy to be described, can account for 

 differences to an amount of some niG.^) The tubes were opened 

 outside the thermostat; the outer walls then cooled down a few 

 degrees, while the inner tubes remained a little warmer. In those 

 few moments a' small quantity of water could distill to the wall of 

 the great tube, and this may be the cause of the loss of weight. 



Now in oi'der to exclude adsorption we have passed on to another 

 arrangement. We had a cylindrical box made of brass (measures: 

 diameter 7.5 cm., height 7.5 cm., volume 320 c.c), which was 

 closed by an exactly fitting brass lid that could be still more strongly 

 fixed on by screws. Both the box and the lid were silvered at ihe 

 inside. The apparatus was entirely plunged into a thermostat, kept 

 constant within 0°. 1 . In tfiis apparatus too we began with weighing- 

 bottles, which only contained wafer; we again had to state a loss 

 of weight. With these experiments the vessel was taken out of the 

 thermostat, and was quickly unscrewed after which the weighing- 

 bottles were taken out and weighed with their stoppers closed. 

 When a closed weighing-bottle with water was placed in the vessel. 

 the weight remained constant ; when taking it out, some slight 

 moisture was to be seen against the stopper. A refrigeration evidently 

 took place here, by a colder stream of air entering when the lid 

 was taken off. In order to axoid this as much as possible, we placed 

 the apparatus rather high in the thermostat; when it had to be 

 opened we made the water run out of the thermostat through a 

 siphon, so far that the lid appeared just above the watersurface. 

 Meanwhile the screws were unscrewed so that the lid could be 

 taken off as soon as it was above the waterlevel ; in this way the 

 whole kept the same temperafui-e until the very last moment. The 

 then obtained results were satisfactory (cp. table V), and we there- 

 fore repeated our experiments with gelatine- water, agar-water, and 

 celloidin-alcohol in this way. 



From these experiments we learn that gelatine, agar, and cellokliii 

 swollen in a liquid, do not undergo a loss of weight when placed 

 in saturated vapour, if the expeiimejit is made rigorously. The results 

 with the celloidin-alcohol system are not so good as with the othei's, 

 it is true, but the decrease which reached an amount of 100 — 200 



^) The greater dilTerenco in the upper lube of llie ord experiment is evidently 

 due to the heating during the sealing process. 



7 

 Proceedings Royal Acad. Amsterdam. Vol. XVII 



