192 Analji/ses of Books. [March, 



mode is that recommended by Mr. Porrett. The quantity of gases 

 being ascertained as usual, the oxide of copper employed in the 

 experiment is to be put into sulphuric acid. The portion of the 

 oxide which has been reduced is thus obtained in a metallic 

 state, and consequently the quantity of oxygen which has been 

 expended may be thus ascertained. Of these methods, the first 

 appears the most simple and least liable to error. 



The above apparatus is susceptible of far greater precision, and 

 is much less troublesome to use than any that has hitherto been 

 recommended for the analysis of organized substances. There 

 may be cases in which its use is inapplicable, but these I am 

 persuaded are few.* 



In conclusion I may observe that I have for several years been 

 engaged in the analysis of organized products, and have at 

 length extended my researches to almost every distinct and well 

 defined substance. The results, when compared with one 

 another, are most interesting, and seem to throw no small light 

 not only on the nature of chemical compounds in general, but 

 upon many important points connected with animal and vegetable 

 physiology and pathology. 



Article VII. 

 Analyses of Books. 



Memoirs of the Literari/ and Pliilosnphical Socicti/ of Manchester^ 

 Second Series. Vol. III. 1819.^ 



{Concluded from j). 141.) 



VI. On the refractive Poivers of Muriatic Acid and Water. 

 By Mr. Henry Oreighton. — The author, during a course of expe- 

 riments on the application of different fluids to the formation of 

 compound lenses, with a view to correct aberration, was led 

 from Dr. Blair's observations to notice particularly the effects of 

 muriatic acid. He was surprised to find that when such a com- 

 pound lens was used, the focal distances were proportional to 

 the specific gravity of the muriatic acid employed. The following 

 table exhibits the focal distances with acid of different strengths. 

 The first column exliibits the specific gravity of the acid 

 employed, the second column the focal distances, and the third 

 column the specific gravity calculated from the supposition that 

 it is proportional to the focal distance. The focal distances of 

 the two double convex lenses were about 24 and 27 inches 

 respectively ; when placed together in the frame about 13 ; 



* The annexed sketch represents the appariilus just as it was ori^iually con- 

 «truc(ed. Perhaps it might be improved by havins;, iflstead of the dish, H, au 

 oblong vessel furnished at one end wilh a deep well for equalizing the height of 

 the mercury on both sides of the graduated tube, K, in which luje the external lubc^ 

 I, as w*U as the gasometer, fig. 3, would be uuneccssary, 



