proceedings of the polytechnic association. 433 

 Analysis and Manufacture of Salt. 



Prof. Joy, of Columbia college, exhibited the constituents ol' common f 

 salt, sodium aild chlorine. He said, to make 100 parts of common salt, it re- 

 quires 39.32 of the metal sodium and G0.G8 of chlorine gas. Sodium is 

 lighter than Avate.'- and swims on it. It has a metallic lustre, and rusts 

 very rapidly, so that it has to be kept under naptha. If water was used, 

 it would take the oxygen from the water. In reference to the manufacture 

 of salt, there are three different methods employed. The first is by evapo- 

 ration of the salt water of the ocean. This method is pursued priucipally 

 in France. There are some thirty of these manufactories there. The gus- 

 tom is to take the water from the salt marshes at high tide and overflow 

 some thousands of acres, and then allow the evaporation to take place in 

 the open air. Of course the evaporation is delayed by rain, which, when 

 excessive, they draw the water off and evaporate by fire. Although the 

 water of the ocean contains but two and a iialf per cent, of salt, yet there 

 are other products arising from its manufacture that makes the process 

 economical. The same process is pursued in Germany. 



The second method of making salt is that adopted near the city of 

 Cracow. The salt mines there were discovered in 1251. The mines have 

 been traced twelve miles in length, and 1,200 feet thick. The salt in the 

 mines is not pure, so they dissolve it and pump it up. The same process is 

 pursued at Haller, where a peculiar tribe called " Wens," have the monopoly 

 of working the mines. At these mines you enter them on the top of a moun- 

 tain and come up in a valley, and you are ferried over several salt lakes, 

 which are found here and there flowing over their crystal beds. They have 

 a very curious way of going into the mines; it is very characteristic. When 

 you wish to descend you enter a building at the top of the mines, where yoxx 

 are furnished with a leather apron, which you proceed to put on, as a black- 

 smith would, before you, but that is not the way, as you are told to put the 

 apron behind, and you slide with this under you down an inclined plain into 

 the mine, holding on to a rope, while your hands are covered with gloves 

 to prevent the skin from being torn off. 



The third method of making salt is from brine, and that is the method 

 jnirsued in this country. The water is put into large pans, and allowed to 

 evaporate; the salt is then formed in small crystals, which are raked out, 

 and the pans filled again. 



The method adopted for evaporating the salt water in Germany is called 

 graduati(jn, which consists of an immense pUe of twigs hundreds of feet 

 high. The water is pumped to the top of this and let trick|e down, which 

 evaporates the water very rapidly. If the wind is strong the evaporation ^ 

 is increased from three to four per cent. In time, however, these twigs 

 become coated with gypsum. 



Soda ash is largely manufactured from salt. In 1852 England produced 

 3,000 tons. Tiiey also manufacture 400 tons of bleaching soda every week. 

 There are at least 10,000 workmen engaged in that manufacture there. In 

 the manufacture of sulphuric acid thej'^ now obtain their sulphur from Iron 



[Am. In-st.] B* 



