1 82 MR. S. BGHT7KCK ON THE 



renders its necessary to avoid distilling the solutions or 

 evaporating them at any but the usual temperature. On 

 the other hand, the length of time necessary for the spon- 

 taneous evaporation of the watery solution produces in a great 

 measure the same effect as the evaporation of the solution 

 at a higher temperature during a shorter period of time. It 

 therefore became necessary to devise some means of pro- 

 ducing a more rapid evaporation of these solutions without 

 the application of artificial heat. This object was attained 

 by means of a simple apparatus, in which a rapid current 

 of air was made to pass over a large surface of the liquid 

 to be evaporated, and which may be described in a few 

 words. 



The solution to be evaporated is poured into a dish or 

 tray of block tin about 16 inches square with perpendicular 

 sides 2 inches deep, and capable therefore of containing when 

 full nearly two gallons of liquid. The dish is placed on a 

 shelf fixed at a convenient height in a wooden box of which 

 abed, Fig. 1, represents the front. This box is closed at 

 the two sides, but open at the front and back from the shelf 

 upwards. It must be sufficiently wide to allow the dish to 

 slide easily in and out, but from front to back it must be so 

 deep as to leave a space of about £ an inch between the 

 front and the dish. At the distance of about 1 J inch from 

 the back of the box there is fixed in a perpendicular position 

 a board /, the upper and side edges of which are firmly 

 attached to the top and sides of the box. The lower edge of 

 this board is about on a level with the upper edge of the tin 

 dish and is accurately fitted to a shelf g, which is suspended by 

 means of two upright pieces of wood h h, 2| inches deep, rest- 

 ing on two ledges * t, fixed to the sides of the box. The spaces 

 between h h and the side walls of the box must be sufficiently 

 wide to allow the sides of the tin dish to move easily up and 

 down in them. By means of supports n n inserted between 

 the tin dish e and the shelf o the former may be raised so as 



