14 CASEIN. 



brass, bronze, nickle-plate or porcelain, or coated with vul- 

 canite or enamel, as well as tinned, lead-lined, galvanised 

 or silver-plated. A vulcanite lining is recommended for all 

 materials which should not be brought into contact with 

 metal, or where the metal used cannot properly resist the 

 action of acids, etc. For these purposes vulcanite is superior 

 to porcelain or earthenware linings on account of its lightness, 

 so that the machine can be run at the highest speed permis- 

 sible for centrifugal separators, whereas with earthenware 

 the heavy weight necessitates low rates of speed. The same 

 applies to lead-lined drums, in which, owing to technical 

 difficulties, a uniform lining cannot be secured with sheet 

 metal less than about one-eighth inch thick, thus making 

 the drum so heavy that it cannot be run without danger at 

 the ordinary speed. 



The washing and draining of the curd is repeated several 

 times, until the washings run away clear, the curd being 

 finally drained in the separator and pressed, if necessary, to 

 bring it to the proper state of dryness. In this form it can 

 be sent out for various uses, in which the presence of the 

 residual moisture does no harm ; or else it is thoroughly 

 dried for conversion into powder. 



The drained curd may be dried on trays in heated drying- 

 rooms, fitted with ventilating appliances to facilitate the 

 removal of the moisture, or else is treated in special forms 

 of apparatus, a few of which will now be described. The 

 first of these is the drying cylinder, warmed from inside or 

 outside, or both, and rotated to keep the contents in constant 

 motion. The cylinder may be provided with a shaft carrying 

 paddles or similar devices and rotating in the fixed cylinder 

 or left stationary while the cylinder revolves ; or the two may 

 move in the same or opposite directions. The best type of 

 drying cylinder is one containing no moving internal parts, 

 since these parts are liable to become obstructed, and even 



