452 Berzelius's Attack on Dr. Tlkomson. 



of carbonate of zinc dried at the temperature of 212° Fahr. 

 As this carbonate, when heated to redness, yielded 20*37 of 

 oxide, it was anhydrous and neutral. The filtered solution 

 was boiled, and the oxide of zinc which subsided, after being 

 collected and ignited, weighed 4*54 grains. The solution was 

 then evaporated to dryness in a porcelain vessel, and the salt 

 again dissolved in water; when some oxide of zinc remained, 

 which, when dried at a red heat, weighed 0*431. The solution 

 was then again evaporated to dryness, and the residue ignited ; 

 and on being dissolved in water a little silicate of zinc was 

 left, which after decomposition yielded 0*22 grains of oxide of 

 zinc. To the remaining alkaline solution, after being neutra- 

 lized by muriatic acid, a few drops of hydro-sulphuret of am- 

 monia were added, which threw down a quantity of sulphuret 

 corresponding to 0*65 grains of oxide of zinc. All these five 

 portions together make up the sum of 26*211 grains, the weight 

 of five atoms of oxide of zinc; so that 5*245 is the weight of 

 one atom. Thomson, on this occasion, does not appear to 

 have reflected on the fact, that neutral carbonate of zinc is 

 never obtained by precipitation from an alkaline carbonate ; 

 and he has left this difficult point unexplained. The reason why 

 all the oxide of zinc contained in a solution cannot be precipi- 

 tated in the cold, is, that a portion is dissolved in the form of bi- 

 carbonate, while that portion of oxide which loses its carbonic 

 acid, subsides in the form of a subcarbonate. We have seen 

 in the experiments of Boussingault, that even the sesquicar- 

 bonate of soda precipitates a subsalt. Consequently, the state- 

 ment as to the nature of the first and largest quantity of the 

 precipitated oxide of zinc is obviously erroneous. And such 

 is the method and result of one of the fundamental experiments 

 on which Thomson's whole system stands, by which he ob- 

 tained more accurate results than any preceding chemist, and 

 through which he established for ever the atomic weights of 

 bodies. The character of this work of Thomson's ought to 

 exclude it from notice here ; but it appears to me, that love 

 for the real progress of science makes it imperative to detect 

 quackery, and expose it to the judgement of every one as it 

 merits." (page 181.) 



We have thought it right to give as nearly as possible the 

 very words of this critique, that scientific men may judge of 

 its tone and merits. With respect to the former, we regret 

 to see the dignity of science sacrificed by the intemperance of 

 those who profess to be her advocates. It well becomes Ber- 

 zelius to expose fallacy in argument, or detect error in analysis; 

 but let him not pass beyond the limits of fair criticism : let 

 him not arraign the character of an individual, who may be 



actuated 



