CASEIN : ITS ORIGIN, PREPARATION AND PROPERTIES. 19 



superimposed steam or hot-water boxes, fitted with proper 

 connections for admitting and discharging the heating fluid, 

 and constructed to stand a working pressure of 5 atmospheres. 

 These boxes support the trays holding the material to be 

 dried. When the rubber-shod doors have been closed, a 

 vacuum of 720 mm. mercury gauge is produced in the case 

 by means of an airpump, the boxes being meanwhile tra- 

 versed by the steam or other 'heating fluid employed. In 

 consequence of the vacuum the water in the material to 

 be dried is vaporised readily at a comparatively moderate 

 temperature (about 104 F.), so that drying is soon effected. 

 In fact, the apparatus will dry in a few hours, and without 

 the slightest risk of overheating, materials which are difficult 

 to dry and take several days when treated by other processes, 

 even if they can be dried at all. The apparatus is easily and 

 conveniently fed, and does its work in a clean and efficient 

 manner. The temperature is regulated by simply setting the 

 steampipe valve. When warm water is used for heating and 

 an efficient vacuum is obtained by means of a vacuum pump, 

 the water can be vaporised at 68 F. A more complete de- 

 scription of drying plant is given by Weigand in his work on 

 this subject. 



PURIFYING THE CURD. 



One hundred parts by weight of well-pressed curd are 

 stirred to a pulp with 50 parts of water, and this is 

 treated, in order to remove lactic acid and butter fat, by 

 steaming for twenty-five to thirty minutes in a wooden vat 

 containing about 150 parts of a 1 per cent, solution of bi- 

 carbonate of soda. 



The vat must be fairly large, on account of the frothing 

 that occurs. After heating, the mass forms a thin milky liquid, 

 which is transferred to a separate vessel to cool, and is then 

 treated with dilute nitric acid until a small sample no longer 



