REPORT OF CHEMICAL LABORATORY 



219 



Analyses of Salt of Native Manufacture 



The process of extraction consists in treating the salt-containing earth with water, Method of 

 drawing oif the more or less clear li(juiil and boiling down in small pans. The cone extraction 

 salt is made by boiling down in a clay mould. It will be seen that the loose salt is 

 both cleaner and purer, but at best is of very poor quality. The sample from El Darner 

 has a dirty appearance. That from Rufaa looks cleaner, but has a brownish colour. 



The salt used by the Government for issue to both men and animals is that imported 

 from Egypt, obtained by the evaporation of the salt lakes near Mex. The analysis of one 

 sample gave the following results : 



Analysis of Salt from Mex 



Insoluble m water ... ... ... ... ... 0-05 percent. 



Calcium sulphate ... 0-62 „ 



Magnesium chloride 008 „ 



Sodium sulphate 0-27 „ 



Sodium chloride (and moisture) ... ... ... 98-98 ,, 



Halt obtained from this source varies somewhat in composition, but will rarely contain more 

 than twice the amount of impurity stated above. 



All the above samples were kindly furnished us by Jlaior Coutts, Assistant Civil ^ 



i^ •' J J > Dongola salt 



Secretary, to whom we are indebted also for the following sample of exceptionally good salt 

 from the desert in the Dongola district, where it is said to exist in considerable quantity. 



Analysis of Salt from Desert near Dongola 

 Insoluble in water ... ... ... ... ... 005 per cent. 



Calcium compounds Traces only. 



Magnesium sulphate ... ... ... ... ... 0-22 per cent. 



True salt 99-73 



The above figures are calculated on the salt free from hygroscojiic moisture. 



I am informed that natron is also found iu the district, and probably the two are derived ^^^^ tionaii 

 from the bed of a natron lake which formerly existed there. When in charge of the Wady pure salt from 

 Natron, in Egypt, it was noticed that at certain seasons of the year it was possible to scrape 

 from the beds of some of the lakes a salt of almost absolute purity. The impurities present 

 were only minute proportions of sodium carbonate and sulphate, not even a trace of calcium 

 nor magnesium being found. The freedom from these was evidently due to the presence 

 of a very large proportion of sodium carbonate in the mother liquor. Salts of the above 

 composition attract moisture from the air only when the latter is excessively damp. The 



natron lake 



