238 CREAMERY BUTTER MAKING 



sufficient to start with so that the air may have an oppor- 

 tunity of escaping with as little loss of ammonia as possi- 

 ble. An additional quantity of ammonia may then be put 

 in each day until the full charge has been introduced. 

 When the ammonia cylinders have been emptied and a 

 charge of, say, seventy-five per cent of the full amount has 

 been introduced, the charging valve is closed and the ex-, 

 pansion valve opened. The glass gauge on the ammonia 

 receiver will indicate the depth of ammonia. The appear- 

 ance of frost on the pipe leading to the coils and the 

 cooling of the brine in the tank will indicate that enough 

 ammonia has been introduced to start with. It is some- 

 times difficult to completely empty an ammonia cylinder 

 without first applying heat. The process of cooling being 

 the same when the ammonia expands from the cylinder 

 into the system as when leaving the expansion valve, a 

 low temperature is produced and the cylinder and con- 

 nections become covered with frost. \Yhen this occurs the 

 cylinder must be slightly warmed in order to be able to 

 get all the ammonia out of it. The ammonia cylinders, 

 when filled, should never be subjected to rough handling 

 and are preferably kept in a cool place free from any lia- 

 bility to accident. The fact that ammonia is soluble in 

 water should be well understood by persons charging a 

 refrigerating system, or working about the plant. One 

 part of water will absorb about 800 parts of ammonia gas 

 and in case of accident to the ammonia piping or machine, 

 water should be employed to absorb the escaping gas. 

 Persons employed about a plant of this kind should be 

 provided with some style of respirator, the simplest form 

 of which is a wet cloth held over the mouth and nose. 



"After starting the compressor at the proper speed and 

 adjusting the regulating valve note the temperature of 



