SODIUM CHLORIDE BERTHOLLET'S LAWS 413 



Europe, deposits of rock salt have long been known at Wieliczka, near 

 Cracow, and at Cardona in Spain. In Russia the following deposits 

 are known : (a) the vast masses of rock salt (3 square kilometres area 

 and up to 140 metres thick) lying directly on the surface of the earth 

 at Iletzky Zastchit, on the left bank of the river Ural, in the Govern- 

 ment of Orenburg ; (b) the Chingaksky deposit, 90 versts from the 

 river Volga, in the Enotaeft'sky district of the Government of Astra- 

 khan ; (c) the Kulepinsky (and other) deposits (whose thickness attains 

 150 metres), on the Araks, in the Government of Erivan in the 

 Caucasus ; (d) the Katchiezmansky deposit in the province of Kars ; 

 and (e) the Krasnovodsky deposit in the Trans-Caspian province. 



A saturated brine, formed by the continued contact of subsoil 

 water with rock salt, is extracted by means of bore-holes, as, for 

 instance, in the Governments of Perm, Kharkoff, and Ekaterinoslav. 

 Sometimes, as at Wergtesgaden in Austria (at Salzkammerhutte), 

 spring water is run on underground beds of rock salt containing much 

 clay. 



If a saline spring or the salt water pumped from bore-holes con- 

 tains but little salt, then the first concentration of the natural solution 

 is not carried on by the costly consumption of fuel, but by the cheaper 

 method of evaporation by means of the wind. For this purpose the 

 so-called graduators are constructed : they consist of long and lofty 

 sheds, which are sometimes several versts long, and generally extend 

 in a direction at right angles to that of the usual course of the wind in 

 the district. These sheds are open at the sides, and are filled with 

 brushwood as shown in fig. 6 4. Troughs, A B, c D, into which the salt 

 water is pumped, run along the top. On flowing from these troughs, 

 through the openings, a, the water spreads over the brushwood and 

 distributes itself in a thin layer over it, so that it presents a very large 

 surface for evaporation, in consequence of which it rapidly becomes con- 

 centrated in warm or windy weather. After trickling over the brush- 

 wood, the solution collects in a reservoir under the graduator, from 

 whence it is usually pumped up by the pumps P P', and again run a 

 second and third time through the graduator, until the solution reaches 

 a degree of concentration at which it becomes profitable to extract the 

 salt by direct heating. Generally the evaporation in the graduator 

 is not carried beyond a concentration of 15 to 20 parts of salt in 

 100 parts of solution. Strong natural solutions of salt, and also the 

 graduated solutions, are evaporated in large shallow metallic vessels, 

 which are either heated by the direct action of the flame from below 

 or from above. These vessels are made of boiler plate, and are called 

 salt pans. Various means are employed for accelerating the evapora- 



