X, A, 6 Cox and Dm- Juan: Salt Industry and Resources 391 



in the side of the mountain highly charged with carbon dioxide, 

 under which condition it carries, besides 3.2 per cent of salt, 

 large quantities of lime and some iron in solution. On reaching 

 the surface, where the pressure is released, the carbonate of 

 calcium is deposited, and in this way the springs have built up 

 huge mounts of mineral deposits. 



A portion of the water is collected and carried nearly 2 kilo- 

 meters through troughs made of split bamboo. These are very 

 rapidly coated with sulphate and carbonate of calcium in that 

 portion of the line nearest the spring, the amount of coating 

 decreasing fairly rapidly with distance. In fact, the objects of 

 carrying the water so far through open troughs are to get rid 

 of the undesirable substances which precipitate before the salt 

 and also in order that firewood may be closer at hand for the 

 boiling. 



Hardwood logs are used for fuel and are shoved in from both 

 sides of the furnace, so that the points meet at the center. As 

 the points burn off, the logs are shoved in farther. Practically 

 the only cost of producing salt here is the cost of getting out 

 the wood. About 70 pans were in operation in June, 1911. 



Only a small part of the water which is at present flowing from 

 these springs is utilized, yet it furnishes 125,000 kilograms of 

 salt annually for a population of about 50,000 people. Thus 

 there ought to be an opportunity for doing away with kettles 

 and open pans and starting a modern concentration plant with 

 steam heat. 



There is some coal in Nueva Ecija, and coal is as good as fuel 

 and is even better for salt vacuum pan or grainer units than 

 wood. In general, when kettles and open pans are used, they 

 are placed over a long combustion chamber in direct contact with 

 the flames from the furnace. Steam heat is more frequently 

 used when vacuum pans are employed. The grainer process 

 requires steam heat exclusively. The steam is carried through 

 pipes submerged in the brine. The temperature is varied by 

 varying the pressure, so as to obtain salt having the desired grain. 

 This process is now much more generally used in the United 

 States than any other. The removal of the gypsum depends 

 upon a quiet, regular boil of the liquid, which cannot be uniformly 

 obtained in all the kettles of a block, and therefore the quality 

 of the salt is variable. Furthermore the heat causes the calcium 

 sulphate to form a scale, which clings to the kettle and thus 

 reduces the efficiency. The general result is that a better quality 

 of salt is produced, and about 50 per cent more evaporation is 



