A F F 



WMtusUy d*c>»mpor* f«cli other, forming nllr«t of llnw and 



atrciiti: of poiadi. but by the Tublc_ _ 



Q^Licfccnt afiinitiej = 58 + i9=i;77 

 Divcik'iit afSnities =444-25=70 



The Table, ihcrcfort;, in this iiillancc, is erroneous. 



Nitnit of foda .ind muriat of ammonia mutually dccom- 



pofe each other ; but by the Table, 



Qiiicfccnl afTinilies = 50+21=^71 

 Divellcnt affinities = 384-31=69 



Nttrat of potafli and fulphat of ammonia mutually de- 

 coiiipufe each other ; but by the Table, 



Qiiicfcent afTinities = 58+46=104 

 Divellent affinities = 384-62 = 100 



Hence is obvious the great probability of en-or in all cal- 

 culations and rcafonings founded on thh Table. 



Mr. Kirwan's numerical fyftem of affinities is founded on 

 the proportion of bafe necjflaiy to faturate a given quantity 

 of acid ; and as no one has treated this important fubjedl 

 with fuch unwearied abihty and profound invelligation as 

 the learned prelidcnt of the Royal Iriih Academy, it will 

 be necedar)- to enter fomcwliat minutely into an examination 

 of the fundamental parts of his fyftem. 



The firll objetl with Mr. Kirvvan was to afcertain exaftly 

 the quantity of rea/ acitl in each of the three mineral acids, at 

 a determinate fpccific gravity (by real acid is to be underftood 

 acid free from all water, except fuch as is necefTary to its 

 ver)' conilitution). For this purpofe, afTuming that mu- 

 riatic acid, in the foim of gas, is free from all mixture with 

 water, he procured 100 cubic inches of this acid gas, and 

 found its weight to be = 60 grains, the barometer ilanding 

 at 29.6, and the theixiometer at 57°. The barometical 

 prelTurc remaining the fame, and the temperature being 

 = 49°, he found that 10 grains of water abforbed an equal 

 weight of muriatic acid gas, and the liquid acid thus formed 

 occupied the fpace of 15. j grains of water ; hence the fpe- 

 cific gravity of this acid was equal to about 1.5, and that of 

 a muriatic acid equal in purity to the acid gas, and of the 

 fame degree of condenfation as the real acid contained in 

 the above mentioned hquiJ acid, would be equal to 3.03. 

 Taking this, therefore, as the fpecilic gravity of real 

 muriatic acid, he next eftablilhed the proportion of this 

 contained in muriatic acids of different fpecilic gravity. 

 Not being able to obtain nitric or fulphuric acids in a ftate 

 of gas, he calculated the proportion of real acid contained 

 in diele liquors, upon the fuppofition that equal quantities 

 of the three acids, reduced to the ftate of real acid, required 

 equal weights of potafti for their faturation : the refults of 

 thefe calculations being found to accord with the aftual 

 fpecific gravities of thefe acids, diluted with different known 

 quantities of water, he hence inferred the truth of the 

 principle that he had affumed. Proceeding from thefe data 

 he next afcertained the quantity of real acid, and real bafe, 

 in all the falls formed by the three acids, with alkaline and 

 earthy bafcs, and comparing thefe refults with the known 

 order of affinity of the bafes for the acids, he drew the 

 general conchuions, " That the quantity of real acid ne- 

 " ceffary to faturate a given weight of any of the bafes, is 

 " in an invcrfe ratio to the affinity of the bafes with the 

 " acid ; and that the quantity of any of the bafes neccffary 

 " to faturate a given quantity of any acid, is in the direft 

 " r^tio of the affinity of the fame acid with the bafe." Or 

 in other words, that, of two bafes, which has the ftrongeft 

 affinity for any given acid, requires the leaft quantity of 

 acid for its faturation ; and a given quantity of acid \viU 



AF F 



tnke up n greater cjiiantltv of one bafe than of another, in 

 proportion to the force of its affinity for the bafe. 



If thefe dedudliona are legitimate, the following Table, 

 containing the qnantities of bafe required to faturate 1 00 

 parts of real acid, is alfo a true exprelfion of their vefpeftive 

 forces of chemical affinity. 



Mr. Kirwan's method has, however, been examined with 

 much care, by two of the ableft chemical philofophers that 

 the age can boall of, M. M. Morveau and Benhollet ; and 

 a number of veiy ferious objtftions have been brought 

 againll it. Thefe may be divided into thofe v/hich call in 

 queftion the eflential principle of the force of affinity being 

 in direft ratio to the quantity of bafe, and thofe which only 

 relate to the accuracy of particular experiments. 



The etfential objeiilions are contained in the following ex- 

 periments of Morveau. A quantity of fulphuric acid 

 containing, according to the table of Kirwan, 100 grains of 

 real acid, required, for faturation, 201 grains of cryltallizcd 

 carbonat of potafti. A quantity of nitric acid, containing 

 alfo, according to Kirwan, 100 grains of real acid required 

 302 grains of the fame fait for faturation. A quantity of 

 muriatic acid, containing 100 grains of real acid, required 

 905 grains of the fame fait. Hence it appears either that 

 Mr. Kirwan's fundamental calculations are erroneous, or 

 that the very principle of his whole lyllem is falfe : for not 

 only do equal quantities of real acids require for their fa- 

 turation different quantities of the potafti, but the quantity of 

 bafe required is in an inverfe ratio to the force of affinity, 

 being exaftly the reverfe of the principle that Kinvan lays 

 down. 



Again, according to Kin\-an's correfted tables, 



Sulphat of potafti confifts of |^™'j^ ^^ 



Sulphat of lime 

 Nitrat of potafti 

 Nitrat of lime 



f Acid 100 

 \ Lime 80.6 

 f Acid 100 

 t Potafti 83.33 

 JAcid I 

 (^Lime 



00 

 34-4 



Now, if a folution be made in water of fuch a quantity of 

 fulphat of potafti as contains 100 grains of real acid, and to 

 this a fufficient quantity of nitrat of hme be added to con-' 

 vert the whole of the fulphuric acid into fulphat of lime, it- 

 is evident that 80.6 grains of lime will be required, and 

 234.4 grains of nitric acid will be fet at liberty ; but this 

 quantity of nitric acid would require for faturation 105.32 

 grains of potafti, whereas fhe decompofed fulphat of potalh 

 will fumiffi only 108.7 grains; there ftiould remain there- 

 fore 64.87 grains of nitric acid in excefs, or uncombined. 

 6 with 



