Observations on the pot-ash brought from America : With respect to its goodness, sophistication, &c. Verified by experimental examination: together with instructions for determining the comparative value of any parcel, by expedient methods: to which is subjoined, processes for making pot-ash and barilla, in North-America. The whole communicated to the society for the encouragement of arts, manufactures and commerce, by R. Dossie: and printed, at their request, in consequence of an application made to them on these points, by the Hon. House of Representatives of the province of Massachusets-Bay.