328 Analysis of Scientific Books. 



tallic, and of the hydrated oxides. The fourth describes the com- 

 binations of simple combustibles with the metals. The fifth con- 

 siders the bodies which result from the combination of acidifiable 

 principles with hydrogen or oxygen; viz., acids. To this chapter 

 an appendix is subjoined, in which the combination of hydrogen 

 with oxygen, and that of hydrogen with azote are discussed. 

 Water and ammonia are here meant. The compounds resulting 

 from the combination of the acids with the salifiable bases (salts), 

 occupy the sixth chapter. The seventh is devoted to animal and 

 vegetable products. In the eighth the manner of preparing and 

 preserving the re-agents described in the preceding chapters is 

 treated of; and the ninth contains some examples of the applica- 

 tion of re-agents to analysis. 



It is by no means our intention to follow the steps of our authors 

 through their tedious common-places ; nor shall we expend cri- 

 ticism on their vicious arrangement. We would rather use their 

 worii as the vehicle of communicating some practical remarks on 

 the important subject which they have, without due preparation, 

 taken in hand to discuss. 



Analytical chemistry may be simply qualitative, or it may be 

 likewise quantitative. To apply the former to an untried form of 

 matter is an exercise of invention, and success in it is the prero- 

 gative of chemical genius. In this department, a mind guided by 

 the routine of rules will be frequently at fault. To determine pro- 

 portions is, perhaps, more irksome and laborious ; but, for the most 

 part, it requires much less ingenuity. Circumstances may occur, 

 however, where the research of quantities may call forth no little 

 invention. Two of the best examples to this purpose are to be 

 found in Sir H. Davy's work on Nitrous Oxide and M. Gay- 

 Lussac's Memoir on Prussic Acid. 



Re-agents, as extemporaneous indicators, belong chiefly to qua- 

 litative analysis ; but they may, without the use of the balance, by 

 due care, throw considerable light also on quantity. This two- 

 fold application of tests was much considered by Bergman and 

 Kirwan ; but it has been almost wholly overlooked by MM. Paycn 

 and Chevallier. 



To describe a chemical body is merely to detail its relations to 

 other forms of matter, supposed to be previously known. An 

 enumeration of these relations constitutes, therefore, the properties 

 of the body. Hence a re-agent is a known substance, which, pos- 

 sessing some marked relation to another substance, serves, by its 

 action with it, to ascertain its general and specific place in a che- 

 mical arrangement. In this extended sense the electroscope, com- 

 mon and voltaic, as well as the magnetic needle, and some optical 

 instruments, deserve to be ranked among tests, though the term is 

 usually restricted to chemical agents. 



We conceive tliat the proper order of discussing the subject of 

 chemical tests would be-; first, to describe in succession the various 



