524 Report on the Salt Range, [Nov. 



on the shales. The kiln being well lighted, fresh layers of shale and 

 brushwood are added, and when the whole has attained the height of 30 

 or 40 feet, it is left to burn, 6 or 8 months being generally sufficient to 

 effect the thorough decomposition of the mass, which when completed 

 has a brick-red color from peroxidated iron, its surface being covered 

 with an efflorescence of alum, containing a large proportion of sulphate 

 of iron or green vitriol. 



Preparation of the Alum. — Close to the kiln, and on a level a little 

 below its base, there is a baked earthen vat 12 ft. square by 1 ft. 5 in. 

 deep. Into this a portion of the burned shale is thrown and lixiviated 

 with water for several hours, which rapidly acquires a dark brown color. 

 "When a saturated solution of the soluble matter in the shale is obtained, 

 it is drawn off from the vat by an aperture in its side (which during the 

 lixiviation is stopped by a plug), into another vat of similar size, but on 

 a lower level. Here the crude alum liquor is allowed to deposit any 

 mud which it may contain, and is then run off into a third but smaller 

 vat on a still lower level, where it is again allowed to deposit any remain- 

 ing impurities. From this it is transferred into an iron evaporating 

 pan, where it is rapidly boiled and mixed with a brownish impure salt 

 called Jumsan, from which it derives alkali necessary to convert the 

 crude alum into an alum of commerce. When a proper quantity of 

 this has been added, which is judged of from the appearance of the 

 liquid, the whole is allowed to settle, and the clear brown alum solution 

 removed into vats, 8 ft. 8 in. long, 5 ft. 5 in. broad and 1 ft. 5 in. deep, 

 a series of which are arranged beneath a shed, close to the evaporating 

 pan. In these the solution, which is concentrated to a point a little 

 short of that of crystallization, is allowed slowly to crystallize for several 

 days. During that time small alum crystals are formed of a slightly 

 pink color, derived no doubt from the impure mother liquor which con- 

 tains a quantity of muriate and sulphate of iron. When a considerable 

 crop of alum has separated, the crystals are removed from the vat, 

 slightly washed with cold water on a sirkee frame and allowed to dry, 

 These are afterwards fused in an iron pan, in their own water of crys- 

 tallization, and when in a fluid state, are removed into large conical 

 earthen jars or gurrahs, 1 ft. 8 in. deep, the same breadth at the shoulder, 

 and 6 inches wide at the mouth, where for eight or ten days they are al- 

 lowed to crystallize. At the end of this period a hole is made in the mass 



