CONDENSED MILK CONDENSING 93 



rapidity of evaporation only as long as enough water passes 

 through the condenser to maintain a high vacuum. As soon as 

 the steam pressure in the jacket and coils reaches the point where 

 the water in the condenser fails to. promptly reduce the vapors/ 

 the vacuum drops, the temperature in the pan rises and evapora- 

 tion is checked. 



The condensing of milk requires immense quantities of water ; 

 experience has shown that it takes from one to three gallons of 

 water to condense one pound of fresh milk, the exact amount 

 depending on the construction of the condenser and the tempera- 

 ture of the water. The water supply is one of the weakest links 

 in most condenseries, so that economy of water is one 

 of the important factors to be considered. The steam pressure 

 in the jacket and coils should, therefore, be so regulated as to 

 make it possible to maintain the maximum vacuum consistent 

 with reasonably economic use of water. With a vacuum of 

 twenty-five inches the temperature in the pan is about 135 de- 

 grees F., the temperature varying somewhat with the altitude 

 of the factory. In some condenseries the temperature of the pan 

 is kept at 150 degrees F. This practice may economize the water 

 a trifle better, but the rapidity of evaporation is considerably 

 lower. 



Condensing at temperatures lower than 130 degrees F., with- 

 out reducing the steam pressure in the jacket and coils, increases 

 the rapidity of evaporation, but taxes the water supply beyond 

 the reach of most condenseries. vSo much water has to be used 

 in the condenser that it is not used economically, as is show r n by 

 the relatively low temperature of the water discharging from the 

 condenser. The temperature of the condenser discharge bears 

 a direct relation to. the temperature of the vapors in the pan. 

 Observations made in various factories and under different con- 

 ditions by Hunziker and others sho\ved that the condenser dis- 

 charge was anywhere from 5 to 25 degrees F. lower in tempera- 

 ture than the vapors in the pan. the difference averaging about 

 15 degrees F. 



The smaller the difference in temperature between the con- 

 denser discharge and the vapors in the pan, the more economic 

 is the use of the water and vice versa. It is not advisable under 



