86 Rusk: A constant teiuperaturc oven for paraffin imbedding. XXIX, 1. 



When the apparatus is to be set up, to furtlier prevent lieat 

 loss, a layer of sbeet asbestos is applied. A pattern is ciit in one 

 piece , from sbeet asbestos, of sucb dimensions that it will cover 

 top, sides, and back, also allowing for overlapping at tbe edges, so 

 securing greater lixity of the covering, This is tben laid on and 

 moulded to tbe surface by soaking witli water and pressing down 

 lirnily. Finally , the doors are covered on the outside Avith the 

 asbestos and a Aap is allowed to extend over the edges where it 

 acts to form a snug contact surface all around the door. 



With the cartridge placed and the current connections made it 

 takes aboiit an hoiir to heat the apparatus to 56*^. Above this 



CA B 



point it cannot go so long as acetone is present. With a good 

 rertux condenser , there is practically no loss of acetone, the appa- 

 ratus as described requiring no replenishing since its Installation 

 about a year ago. The araount of acetone need be only as much 

 as will cover the heating unit. In a word all forms of electric or 

 mechanical thermoregulation are doue away with. 



Acetone is of course inflammable ; little of its gas, however, can 

 escape through the condenser and under any ordinary conditions of the 

 laboratory its use is certainly as safe or safer than the use of gas. 



The measurements here given may of course be varied to meet 

 requirements and undoubtedly an oven embodying the same method 

 of regulation may be made several times as large if additional 

 electric units are provided. 



[Eingegangen am 6. Mai 1912.] 



