VOL. XX XIX. J PHILOSOPHICAL TKANSACTIONS. 11 



liquor be evaporated a little too much, there will be no crystals of salt formed, 

 but the liquor will be converted into a hard transparent mass, not unlike glue. 

 But by dissolving this mass again, it is made to crystallize, as on dissolving 

 M. Seignette's salt. 



This salt purges very well, from I to 2 oz. dissolved in a quart of water. 



M. GeofFroy employed himself in perfecting this salt, and in examining the salt 

 of kali, and comparing it with borax. From the salt of kali he extracted Glauber's 

 salt, by mixing it with oil of vitriol. He next made experiments on borax. A 

 mixture of 4 oz. of borax with 1 oz. and I dr. of vitriol, on sublimation, gives 

 the sedative salt, described by M. Homberg ; and the residue exposed to a 

 strong fire, afforded Glauber's salt.* M. GeofFroy found out a method *o 

 shorten this operation : for, instead of subliming this salt, he procured it by 

 crystallization in light foliated laminae. This salt, whether sublimated, or 

 crystallized, has the property of dissolving in sp. of wine ; and when this sp. of 

 wine is set on fire, its flame is green. Sp. of wine has no effect on borax ; the 

 oil of vitriol, digested with sp. of wine, communicates no greenness to its flame; 

 it is therefore requisite that the borax be united with an acid, in order to pro 

 duce this green flame. 



Sedative salt, made by crystallization, crystallizes in a peculiar manner : this 

 operation is performed with 4 oz. of borax, 1 oz. and 1 dr. of concentrated oil 

 of vitriol, the most fixed and weighty that can be had. The borax is put into a 

 glass retort ; the oil of vitriol is poured on it ; and then -J- oz. of common water. 

 This mixture being exposed to a fire, gradually increases, after the phlegm has 

 passed off, and even while it is passing there rise flowers, or a volatile salt, in 

 very beautiful foliated laminae, some of which melt by the heat of the fire. 

 After the operation, the finest of these flowers, which are round the neck of 

 the retort, are gathered ; and those that are grey are thrown on the remaining 

 mass ; which mass is dissolved in water, filtrated and evaporated slowly. Some- 

 times even without evaporation, the shining talcous laminse are to be seen in 

 the liquor. In 24 hours the liquor is poured from these laminae ; they are washed 

 in fair water, set to drain, and then to dry in a stove. -j~ 



If these crystals do not calcine in the stove, or in the sun, it is a sign there 

 is nothing crystallized but the sedative salt : if they do calcine, it is a sign that 

 there is some Glauber's salt mixed: and then this salt must be dissolved again in 



• Borax being compounded of a peculiar acid termed boracic acid and soda, its own acid is ex- 

 pelled from the alkaline base by the vitriolic or sulphuric acid of the vitriol here employed ; which 

 unites with the said alkaline base, and forms with it Glauber's salt, i e. sulphate of soda. 



t The product here termed sedative salt, is now known to be the acid of borax. 



02 



