A F F 



A F F 



TABLE TIL Continued. 



Of thefe Tables, the firfl is a tranfcript of the original 

 one, pubUilied by Geoffroy, and which merits prefcrvation 

 as an hillorical memorial of an important xra. in chemical 

 fcience. The fecond and third are, with a few alterations, 

 copies of- Dr. Pearfon's enlarged edition of Bergman's 

 tables. 



Table II. contains the eleftive affinities, as far as they 

 have been afcertained, of fixty of the moll important che- 

 mical fubllances. All thefe take place through the medium 

 of water, in which one or both the fubftances are diifolved, 

 the temperature therefore, in all the cafes here mentioned, 

 cannot exceed 212° Fahrenheit. At the head of each co- 

 luni, in larger charafters than the reft, and divided from 

 them by a horizontal line, is the name of the fubftance 

 whofe affinities are the fubjecl of the reft of the column ; 

 and thefe are arranged in the order of their intenfity, fo as 

 that the fubftance of ftrongell affinity with that which is at 

 the head of the column, ftands the iieareft to it. Thus in 

 the column of lime, N"^ 8, the fubftances from oxalic acid 

 downwards, prefent a decreafing ferics of the affinities of 

 lime : hence the combination of lime with any fubftance in 

 the column, may be decompofed by any of the bodies tliat 

 precede this fubllance, but is not broken by thofe which 

 fucceed it. The ufe and application of this table is obvi- 

 eus. If, for example, it is required to decompofe an aque- 

 ous folution of muriat of foda (common fait) by lingle af- 

 finity ; the firft inquiry is, which of the two componCiit 

 parts is to be fet at liberty : fuppofe it to be the acid, I 

 am then to find a fubftance wiiofe affinity with foda is greater 

 than that of muriatic acid, for this pur;;ofe I turn to the 

 column of foda N"^ Ii, and find tliat by the addition of 

 either fulphuric or nitric acid, I (liall be able to decompofe 

 the fait in queftlon, fo as to obtain its acid in a difengaged 

 ftate : if, on the other hand, the alkaline bafe is wanted, I 

 find, upon infpcftiug the column of muriatic acid, N^ 18, 

 that the atlinity of potafti for muriatic acid is greater than 

 that, of foda ; and therefore, by this means, I obtain muriat 

 of potafli and free foda. Again, if citrat of lime is to be 

 decompefcd, I find, by referring to citric acid, column 30, 

 that it is impoffible to do it fa as to fet at liberty the lime, 



bqcaufe this ftands the firft in the column of citric acid ; but 

 from the column of lime N^ y, it appears that no lefs than 

 thirteen acids will each of them feparate the lime, fi) as to 

 leave the citric acid difengaged. If the decompofition of 

 fulphat of Barytes is required, it is plain from the column 

 of Barytes, N° 6, that it cannot be decompofed fo as to fet 

 the fulphuric acid at liberty ; it is alfo equally obvious from 

 the column of fulphuric acid, N"^ 14, that the Baiytes can- 

 not be feparated, iulphat of Barytes therefore is undecom- 

 pofable in water by lingle affinity. 



In Table III. the affinities of forty-three fubftances, with- 

 out the medium of water, and at a temperature equal to- 

 tlie fufion of at leaft one of the fubftances in each inftance, 

 are regiftered : the application and conftrutlion of this 

 table is precifely the fame as of the former ; to enlarge more 

 upon it is therefore unneceftaiy : it is curious, however, to 

 obfcrve how the order of affinities is modified by tempera- 

 ture ; for we find that fulphat of Barytes which is unde- 

 compofable by fingle aftinity in water, may at a high heat 

 be decompofed with fcparation of the Barytes, by potafh or ' 

 foda ; and with fcparation of the acid by the phofphoric, 

 boracic or arfenic acids. 



The conftruttion of GeofTroy's tables, although admirably- 

 well fuited to cxprefs the general refults of fingle affinity, 

 is deficient as a metliod of regiftering th.e conclufions from 

 fingle and unconnected experiments ; on which account the 

 fchemes of Bergman, either invented or at leall firft brought 

 into general uie by him, have been univerfally adopted for 

 this purpofe. The regiiler of an experiment in affinity 

 ought not to be confidered as complete, except it expreftes 

 clearly, I4 the refitlt., i. e. whether or not any change is ef- 

 fefted ; 2d, the merjlruum, whether water, alcohol, &c. is 

 the fluid in which the fubftances are diftolvcd : jdly, the 

 tempi-rnture of the fubftances at the time of experiment. 

 4thiy, xWJlate of the new fubftances, whether they are pre- 

 cipitated from the menftruum, or remain diftolvcd, or are 

 fublimcd. Now all thefe circumilanccs are expreffed clearly 

 and concifely in the following fehemes. Suppoie the ex- 

 periment is made to decompole muriat of pota(h in water at 

 the common temperature, by foda, it will be found that no 



change 



