4g6 PHILOSOPHICAL TRANSACTIONS. [aNNO 1 692-3. 



charcoal, dropping pieces of charcoal afterwards into the crucible. It continued 

 about an hour in the melting furnace in fusion, without producing a regulus, or 

 a substance that would apply to the magnet, excepting only what stuck to the 

 charcoal, as in the former experiment. 6. I fluxed another parcel of it with 

 saltpetre and flowers of brimstone, without being able to procure any regulus. 

 7. I poured good spirit of salt on a parcel of this sand, but could observe no 

 luctation thereby produced. 8. I poured spirit of nitre, both strong and 

 weakened with water, on parcels of the same sand, without being able to dis- 

 cover any conflict. Q. I poured single aquafortis on another parcel of it, with- 

 out being able to perceive any ebullition worth noting. 10. I poured double 

 aquafortis on another parcel of it, which for ought I could discover had no 

 more effect on it than the former. 1 1 . I poured also some aquaregia on a 

 parcel of it, without discovering any sensible effect. 12. I poured good oil of 

 vitriol on another of this sand, but seeing no bubbles produced, I weakened 

 the oil with water, but without any sensible effect. And several other experi- 

 ments, with no better success. 



^n Account of the Hon. Robert Boyle's Way of examining JVaters as to Fresh- 

 ness and Saltness. To be subjoined as an appendix to his lately printed Letter 

 about sweetened Sea-Water, Oct. 30, l683.* N° 197, p. 627- 

 When I considered that, as I have found by various trials, divers metalUne, 

 and other mineral solutions, could be readily precipitated, not only by the spirit 

 of salt, but by crude salt, whether dry or dissolved in water, it was no difficult 

 matter for me to think, that by a heedful application of the precipitating quality 

 of common salt, we might discover whether any particles of it, at least in any 

 considerable number, lay concealed in distilled water, or any other proposed to 

 be examined. 



For this purpose, I took some common water distilled in glass vessels, that it 

 might leave its salt, if it had any, behind it, and into 1000 grs. of it, put 1 

 grain of dry common salt : into a convenient quantity, as 2 or 3 spoonfuls, of 

 this impregnated liquor, I let fall a fit proportion, for instance 4 or 5 drops, of 

 a very strong and well filtrated solution of refined silver, dissolved in clean 

 aquafortis ; upon which there immediately appeared a whitish cloud, which, 

 though but slowly, descended to the bottom, and settled there in a white pre- 

 cipitate.-|- 



* N. B. This paper was deposited wish the secretaries of the Royal Society, An. l683, sealed up 

 and opened since the author's death. — Orig. 



t And perhaps it may be proper, that I here observe (what is not wont to be taken notice of.) 

 That divers solutions of mineral bodies may be precipitated by dilution ; that is, (to explain this ex- 



