37O ON SWEETENING SEA-WATEK. 



Whether the distillation be made after Dr. Lind's method, OP 

 with the more simple contrivance of Dr. Irving, the operator should 

 be careful not to continue the process too long, but to stop when 

 three-fourths or only two-thirds of the water shall have been dis. 

 tilled ; as the water which is obtained afterwards is less pure, and 

 the brine sometimes becomes so strong as to corrode the copper 

 boiJer. [It appears from the Bishop of LlandafPs experiments 

 (see his Chemical Essays before quoted) that the water distilled 

 from salt-water is not wholly free from saline particles; but that it 

 probably contains them in so small a proportion as not to injure its 

 salubrity in any sensible degree.] When too much fire is employed 

 it is possible, especially towards the end of the operation, that some 

 muriatic acid may be disengaged, the action of which upon the me- 

 tallic vessels it must be desirable to prevent. This might perhaps 

 be effected by adding some potash to the sea-water. 



[Phil. Trans. Abr. Vol. 1. p. 549, Note of the Editors.'] 



This subject is so important that it has occupied the attention of 

 the chemists of the continent as well as of our own country for these 

 fifty years past. It was at first conceived not only as above stated, 

 that sea-water abounds with bituminous matter, but with ammoni- 

 acal gas from the decomposition of animal bodies of all kinds ; and 

 bnce, iu the process of distilling, means were taken to divest the 

 sea-water of this substance, as well as of its supposed bitumen. 

 Admitting the fact, for which, however, there is no authority, the 

 distilled water, when the process is carefully conducted, as above, 

 will be as free from ammonia as from bitumen. 



One of the earliest writers upon the subject is Mr. Hanton, 

 whose refrigeratory is worthy of notice on account of its simplicity ; 

 for, in order to save the space of a large vessel, in which the worm 

 is generally placed, and the trouble of filling it with cold water, he 

 made it pass through one aperture in the side of the ship into the 

 sea, and return by another, so that tlie sea itself performed the 

 office of a refrigeratory. 



Captain Wm. Chapman, under a great want of water in peculiar 

 circumstances, exhibited an ingenuity, though under the old system, 

 that is well worthy of notice. Sometime in September 1 757, after 

 his crew had been ten days at sea, by an accident (off the north 

 cape of Finland) they lost the greatest part of their water. They 



