Miscellanies. 375 



about the same time observed that not only starch, but several other 

 vegetable substances, produce formic acid, when treated in the same 

 manner. Gmelin procured it from sugar, ligneous matter, althea 

 roots, mucic acid, &c. but it was always soiled, especially when ob- 

 tained from starch, by a substance which might be separated by de- 

 composing its salts by sulphuric acid. 



A very pure acid may be obtained by distilling alcohol with sul- 

 phuric acid and the peroxide of manganese; but to prevent the form- 

 ation of sulphuric ether, it is best to employ diluted alcohol, or com- 

 mon brandy ; for if the alcohol is concentrated, there is formed, be- 

 sides sulphuric ether, formic ether, which not only would diminish the 

 quantity of formic acid, but the latter Would give with lead, a colored 

 salt, difficult to crystallize. Acetic acid, subjected to the same treat- 

 ment, yields no formic acid. The iibrine of blood has produced it, 

 but very impure. 



u 



1 b30 



8. Theory of the Electric Pile. — In the first part of Berzelius' 

 Chemistry, this subject is discussed with the author's usual sagacity. 

 In commenting on the experiments of Prof. De La Rive, who sup- 

 ports the chemical theory, he finds one equally opposed to both the- 

 ories. " If a glass tube be bent in the form of a U, into the one end 

 of which is put sulphuric, and into the other nitric acid, so as to keep 

 them unmixed, and if an arch of zinc and copper be so placed that the 

 zinc shall be in contact with the former, and the copper with the lat- 

 ter, no chemical action takes place in the sulphuric acid, but the cop- 

 per is dissolved by the nitric; nevertheless, the zinc is positive, and 

 the copper negative, contrary to what ought to follow if the chemical 

 action were the source of the electricity." To remove the powerful 

 objection to his opinion to which this seems to give rise, he shows 

 that if the arch consist of one metal only, the direction of the stream 

 is still the same, though its intensity is less. Hence, says he, it is 

 clear that when a single metal produces a stream in the same direc- 

 tion as two, the contact between two, copper and zinc, cannot have 

 been the cause of the stream ; but in his eagerness to overthrow 

 Volta's theory, De La Rive seems to have forgotten that the result 

 of the experiments controverts as strongly the opinion he wishes to 

 support, that the chemical action is the primary cause of the electrical 

 phenomena, since while the chemical action is in the one acid, the di- 

 rection of the chemical phenomena is from the other. He endeavors 

 to explain this on the principle, that the electrical stream finds greater 

 difficulty in passing from the copper to the sulphuric acid, than from 

 the latter to the nitric acid, but that is to let a slight hindrance over- 

 come a powerful action. 



