VAEIOUS METHODS OF PREPARING CASEIN. 27 



else churned with water, which is drawn off after the curd 

 has subsided. After removing a further quantity of water 

 by pressing the curd in a weighted sack or in a press under 

 moderate load, the product, which is still moist, is broken 

 down in a curd mill and is ready for sale in the damp state. 



" Dry " casein is the kind generally wanted for technical 

 purposes. Various forms of drying apparatus may be used, 

 such as the hot-air apparatus for drying vegetables or heated 

 drying chambers fitted with frames for supporting superim- 

 posed trays made of strong canvas, permeable to moisture. 

 These hot-air appliances consume a great deal of fuel and 

 are troublesome to manage unless fitted with expensive 

 mechanical stirring or turning devices, the constant turning 

 and breaking down of the casein being necessary. At the 

 same time a constant drying temperature, between 122 and 

 175 F., must be maintained. For this purpose the follow- 

 ing arrangement has proved very satisfactory and cheap, 

 besides enabling the heat to be well utilised. Two small 

 brick walls, about a foot high, are built, without foundations, 

 40 inches apart, each being topped by a coping of wood 6 

 inches square. The coping is surmounted by a thick strip 

 of damp millboard about 2 inches wide, and this in turn by 

 plates of sheet iron, 40 inches by 80, and ^ inch thick, fastened 

 down by screws, so as to form a long horizontal flue 40 

 inches wide and 12 high. Where the ends of the iron plates 

 join they are supported by wooden traverses to which they 

 are screwed with an intervening layer of millboard as in the 

 case of the copings. The two ends of this flue are closed by 

 brick walls through one of which exhaust steam is intro- 

 duced, whilst an opening in the other enables the steam to 

 escape into a small chimney. The flue should have a gentle 

 slope towards this end so that the condensed moisture may 

 drain away. The casein may be dried very quickly on these 

 iron plates by spreading it out on the farther end and turn- 



