ON PEPPER. ' 15' 



a brittle fubftance is obtained, differini^' in appearance from 

 common ftarch, but exhibiting nearly the fame properties with 

 re-agents. The apparent difference is probably owing to a 

 portion ot" water remaining united to the ftarch. 



* 3. When ftarch is triturated with the hot infufion of nut-^-Completely 

 galls, a complete folution is effeded. The folution is ^^^''^-InM^of gzUs, 

 parent and rather lighter coloured than the infufion of galls, and precip. by 

 When cold it becomes opaque, and a copious curdy precipi-^°^'^* 

 lateralis. 



The infufion of nut-galls, which I am accuftomed to em- The infufion of 

 ploy in all my experiments, except when the contrary is ^'^-^^.^^fa^,^'^^^^^^ 

 prefsly mentioned, is made by boiling together one part of 

 galls in coarfe powder and two parts of water in a glafs retort. 

 When cold, the liquid part is decanted into a glafs phial. It 

 is at firft muddy, and opake ; but on (landing, a fediment falls, 

 and a tranfparent liquid remains of a deep brown colour, 

 which conftitutes my infufion. An ounce meafure of this in- 

 fufion, when evaporated to drynefs in a glafs velTel placed on 

 a tin-plate box, heated by fteam, leaves a brown refidue, 

 which weighs 68 grains. This refidue confifts chiefly of tan; 

 for thegreatefi part of the exlradive gradually feparates from 

 the infufion in the fiate of a brown, tough, imperfectly folu- 

 ble membrane. Neiiher*extra8ive nor pure gallic acidh^^ any --"^ 



effed upon the decoction of ftarch. Hence the precipitate is 

 obvioufly produced by the fole adion of tan upon the ftarch. 



4. Twenty-four grains of fiarch were triturated with half an Experiment of 

 ounce meafure of the infufion of galls, and mixed with about ^^^j.^'J^'^^^j ° 

 five ounces of hot water. A complete folution took place; 

 but on cooling, the liquid became opaque, and a precipitate 

 fell, which dried by a fteam heat, weighed 35 grains. The 

 refidual liquor had a light yellow colour and an aftringent tafte. 

 When evaporated to drynefs, it left a refiduum that weighed 

 17 grains. This refiduum contained ftarch, for it was not 

 completely foluble in alcohol. In this experiment feme lofs 

 muft have been fuftained during the trituration. For the folid 

 matter obtained weighed only 52 grains; or fix grains lefs than 

 the 21' grains of ftarch and the 34 grains of folid matter in the 

 infufion of galls. The following is more to be depended on: 

 After various trials, I found that ftarch and tan are capable of 

 uniting in diflFerent proportions. But the precipitate is leaft 

 foluble when | oz. meafure of infufion of galls is ufed for 

 every 24 grains of ftarch, — I took 24 grains of ftarch, boiled 



them 



