80 



ANALYSIS OF MILK. 



by four holes, one in each corner. The jacket is closed, except 

 for one opening, in which a condenser is placed. About 1 inch 

 from the bottom a sheet of copper is fixed, in which is a round 

 hole of diameter equal to half the width of the interior. 



The jacket is filled with distilled water, which is heated either 

 by a steam coil or a gas flame ; perforated copper shelves are 

 used to support the basins, etc., containing the substances to be 



Fig. 5. — Diagrammatic View o( Air-bath. 



dried. The heating is chiefly done by conduction from the sides 

 of the bath through the shelves ; a current of hot air, approach- 

 ing in temperature to that of boiling water, is always passing 

 through the bath, and rapidly removes the vapour. 



The. condenser is supplied with cold water, and prevents loss 

 of water. It conduces greatly to the efficiency of the bath to 

 use distilled water, as no scale is produced on the coils and sides 



