(98) 
air of the apparatus was exhausted by means of an automatical 
mercury airpomp. This was repeated till the bulbs were free from air. 
In order to comply with Prof. Jann’s wish, I brought about a 
communication between the bulbs with water and solution and one 
of the drying bulbs (filled with H,SO,). When the air is greatly 
rarefied, Hj, SO, absorbs the vapour of water quickly and the water 
and the solution, having the temperature of the room + 20° (the 
bulbs being continually shaken), evaporated quickly, in consequence 
of which the temperature of the water and the solution fell consi- 
derably. To prevent congelation the bulb was now and then warmed 
with the hand. The temperature of the bulb with H,SQ, rose con- 
siderably during this absorption of water, and it was also frequently 
shaken. When the water and the solution had been reduced to the 
half of their former quantity by evaporation, the bulbs were shut 
off from the apparatus. Every solution was first treated in this 
way, after which the bulbs were placed in ice, and the experiment 
began. 
The concentration of the solutions was determined by weighing 
+ 50 gr. solution in a flask with a long neck, and then the water 
was evaporated according to the method applied by Mr. ANDREAE ') 
While the flask was being heated in a waterbath, a weak current 
of air was drawn over the solution. After all the water had been 
evaporated, the flask was placed in an airbath of 170°, while all 
the time a stream of air was drawn over it. In this way it is also 
possible to expel the water from NaCl-solutions without any loss 
of weight of salt. 
I may further add that I had altered the apparatus somewhat 
for these experiments. Instead of two bulbs, I used three; one filled 
with water. and the two others with solution. One of these bulbs 
with solution remained untouched during the whole series and served 
as a test. These three bulbs were placed in a copper trough, which 
was surrounded by a larger wooden one in such a way that there 
remained a space of 6 em. all round. This space was filled up with 
small pieces of ice, while the copper trough was filled with a paste 
of fine ice and water. Two pieces of paste board, which could move 
across each other and were provided with slits, served as a lid. In 
this way I was quite sure of a constant temperature and yet I 
could shake the bulbs thoroughly. 
In order to make it possible to read the manometer more accurately, 
‘) Journ. f. prakt. Chem. 22, p. 456, 1884. 
