EXPERIMENTS ON ASTRINGENT VEGETABLES. 31 



tion from Dr. Tliompfon, by no means all that might be 

 brought, nor dare I venture to hope fo ftated as to be beyond 

 the reach of cenfure. 



Many more curious points rife before the imagination on fo Intended publi- 

 interefting a fubje6t as heat. As I hope, however, foon to be vvritin^s of chg 

 able to lay before the public fome of my father's writings, I late Dr. Irvine, 

 may on that occafion have an opportunity of expreffing myfelf 

 at greater length than I can intrude in your journal. 

 I am, 

 SIR, 



Your obedient humble fervant, 



WILLIAM IRVINE. 

 Bedford-Street, Covent-Garden. 



An Account of fome Experiments and Ohfervations on the Conjli- 

 tuent Parts of certain Aftringent Vegetables ; and on their Ope- 

 ration in Tanning. Bij Humphry Davy, Efq. Proff- 

 for of Chemiftry in the Royal Injlitulion. 



(Concluded from Page 256. Vol. V.; 



IV. EXPERIMENTS AND OBSERVATIONS ON THE AS- 

 TRINGENT INFUSIONS OF BARKS, AND OTHER VEGE- 

 TABLE PRODUCTIONS. 



A HE barks that I examined were furniQied me by my friend Infufions of 



Samuel Purkis, Efq. of Brentford; they had been colleaed in ^^'^' '" :^^*" 

 4U r f ^ C J %u by gentle heat. 



the proper tealon, and prelerved with care. 



In making the infufions, I employed the barks in coarfe 

 powder; and, to expedite the folution, a heat of from 100 to 

 120*" Fahrenheit was applied. 



The ftrongeft infufions of the barks of the oak, of the Lei- Of oak, willow, 

 cefter willow, and of the Spanifh chefnut, were nearly of the a"^ Spamfc 

 fame fpecific gravity, 1 .05 . Their taftes were alike, and ftrong- 

 iy aftringent ; they all reddened lilmus-paper ; the infufion of 

 the Spanith chefnut bark producing the higheft tint ; and that 

 of the Leicefter willow bark the feebleft tint. 



Two hundred grains of each of the infufions were fubmitted were chemkal- 

 to evaporation ; and, in this procefs, the infufion of the oak '^ ^**°"°«<^* 



bark 



