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first Experiment is afforded me by the Dissolution of Sal Armoniac, which I have somewhat wonder'd, that Chymists having often occasion to purifie that Salt by the help of Water, should not have, long since, and publickly, taken notice of. For if you put into three or four times its weight of Water a pound or but half a pound (or even less) of powder'd Sal Armoniack, and stir it about to hasten the dissolution, there will be produc'd in the mixture a very intense degree of Coldness, such as will not be onely very sensible to his hand that holds the Glass whilst the Dissolution is making, but will very manifestly discover it self by its Operation upon a Thermoscope. Nay, I have more than once by wetting the outside of the Glass, where the dissolution was making, and nimbly stir-