480 PHILOSOPHICAL TRANSACTIONS. [aNNO I767. 



with a little honey ; on the surface of which was to be observ-ed a number of 

 globules of the same sort of matter, of the size of mustard-seeds, and interspersed 

 with a black very bitter stuff. Next day, on examining the dark-coloured 

 purplish liquor which he had put into the tea cup, he found that a great part of 

 it had concreted into a very beautiful salt. The crystals were almost all fiat, and 

 seemed in general to assume the form of long, narrow parallelograms, or longish 

 squares. 



, , This salt is pleasant to the taste, and evidently generates cold in the mouth in 

 the time of its solution; but he had not quantity enough to try with a thermo- 

 meter what degree of cold it generated in the time of its solution in water. 

 Sect. iv. — Of Neutral Salts formed with Flowers of Benzoin, and Salt of Amber. 



ExPER. ] and 1. — With the Flowers of Benzoin, Most modern chemists 

 have considered the gum benzoin as a resinous substance, which bears the same 

 analogy to the vegetable resins, as the succinum or amber does to the fossil bi- 

 tumens ; and they have esteemed the flowers of benzoin to be an acid salt,* 

 mixed with an oily and a small proportion of an earthy matter; but have brought 

 no proof of its being so. 



1 . In order to ascertain this fact. Dr. M. put 2^ drs. of the flowers of ben- 

 zoin into some water, and then dropped into it by degrees a solution of the fossil 

 alkali ; every drop raised an ebullition or effervescence, in the same manner as 

 when any common alkaline salt is thrown into an acid liquor. He continued 

 adding the alkaline ley till all ebullition ceased, and the flowers were fully satu- 

 rated and dissolved; after which he filtered the liquor, and evaporated it till a 

 pellicle began to appear, and then set it in a cool place all night, and next morn- 

 ing he had a fine pure transparent neutral salt. It adhered to the china basin in 

 form of a saline crust, which he removed ; and on looking through it in the 

 light, it seemed to be composed of an infinite number of very small crystals; 

 above this lay, in many places, a number of crystals of the figure of small ob- 

 long parallelograms. But from the greater part of the surface of the crust there 

 arose a number of very fine thin delicate plates of irregular figures, standing on 

 one edge ; some were squares, others parallelograms, and others had more sides.-^ 



This salt, when first made, appeared as transparent and clear as glauber salt, 

 or nitre; but on being exposed to the air, became very soon white and mealy. 



In the time of the evaporation of this salt, a saline white mealy crust rose 

 every where on the sides of the china basin in which the operation was per- 

 formed, and even came over so far, as to cover its whole outside. What rose 

 in this manner had a sweetish taste, and was not so sharp in the mouth as what 



* Now known by the name of benzoic acid. 



f In the modern chemical nomenclature the salt thus formed by combining the acid of benzoin 

 with ihe fossil alkali^ is termed benzoate of soda. 



