254> On the Manufacture of Salt in India. 



After providing a large-grained salt for the cure of fish, 

 and other provisions, the next object to which attention might 

 be profitably directed, would be to working up the bittern. 

 At Lymington, in Hampshire, where salt is manufactured 

 from sea-water, partly by boiling and partly by solar heat, 

 pretty much on the plan followed in India, sulphate of 

 magnesia is made from the bittern, which is essentially the 

 same as that which is now lost in our salt works. 



method of analysis adopted in examining the several varieties of Chloride of Sodium, is 

 almost similar to that of Dr. Henry's, and is as follows — : 



" On 1000 parts by weight of the salt, previously dried and pulverized, three ounces of alcohol 

 Sp. gr. 816, and nearly at boiling temperature were poured. To ensure the access of the alcohol 

 to every part of the salt, they were intimately mixed in a mortar. The alcohol was then separa- 

 ted by filtration, and the chloride of sodium washed as it lay on the filter, with 3 ounces more of 

 alcohol. 



" The filtered solutions were evaporated to dryness, and to the dry mass a little fresh alcohol 

 was added. This separated a small portion of the chloride of sodium, which was dissolved 

 with the earthy muriates. The solution was again evaporated, and an aliquot part was dis- 

 solved separately for the purpose of putting it to the usual tests. The chloride of magnesium 

 was alone indicated with but one exception, when it was found combined with chloride of 

 calcium. 



" To the solution of two earthy chlorides, a fully saturated solution of carbonate of ammonia 

 was added, which precipitated the lime as a carbonate ; this was separated by filtration, dried 

 and weighed. To the filtered liquid, a solution of phosphate of soda was added, and the preci- 

 pitate of ammoniaco-magnesian phosphate was dried at a temperature of 90' and weighed. 



" The salt which had resisted the action of alcohol, was dissolved by long boiling in 16 ounces 

 of distilled water, and the solution filtered. A quantity of insoluble matter remained on the 

 filter, which was well washed, dried, and its weight ascertained. To the filtered solution car- 

 bonate of soda was added, and boiled briskly for several minutes, in order that none of the 

 earthy carbonates, which were separated, might remain dissolved by excess of carbonic acid. 



' ' The precipit ated carbonates after being well washed with boiling distilled water, were allowed 

 to subside, and the washings added to the liquid first decanted from the precipitate. To these 

 united liquids, (after the addition of hydrochloric acid in excess to saturation,) muriate of 

 barytes was added. The sulphate of barytes precipitated was washed sufficiently, dried, 

 ignited, and its amount ascertained. 



" To the earthy carbonates excess of sulphuric acid was added in a platina capsule, and evapo- 

 rated to dryness, calcined in a low red heat and the weight of the earthy sulphates ascer- 

 tained. 



" The dry sulphates then were washed with a small quantity of tepid distilled water, and to the 

 solution filtered, was added a fully saturated solution of carbonate of ammonia and phos- 

 phate of soda. The precipitate produced was collected, dried at 90 1 and weighed. 



" It became expedient to examine whether in addition to the sulphates of lime and magnesia, 

 the quantity of which had been determined by the foregoing process, the specimens of salt 

 might not contain also an alkaline sulphate. To decide this point, the amount of the acid 

 dedueible from the weight of the sulphate of barytes was compared with that which should 

 exist in the two sulphates actually found. The result of the examination was such as to lead 

 to the conclusion, that no alkaline sulphate was present." 



