8G Rusk: A constant tomperature oven for paraffin imbedding, XXIX, 1. 



When tbe apparatus is to be set up, to further prevent heat 

 loss, a layer of sbeet asbestos is applied. A patteru is cut ia one 

 piece , from sheet asbestos , of sucli dimensions tliat it will cover 

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

 securing greater fixity of the covering. This is then laid on and 

 moulded to the surface by soaldng with water and pressing down 

 lirmly. Finally , the doors are covered on the outside with 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 ciirrent connections made it 

 takes about an hour to heat the apparatus to 56^. Above this 



A 



B 



poiiit it cannot go so long as acetone is present. With]^a good 

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

 ratus as described requiring no replenishing since its Installation 

 about a year ago. The amount of acetone need be only as rauch 

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

 raechanical thermoregulation are done 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 

 requireraents 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 G. Mai 1912.] 



