52 Notices respecting New Books. 



cumstance he on one occasion especially notices, observing that no 

 nitric acid had been used in preparing it, and consequently that the 

 oxygen could not be derived from the decomposition of nitric acid, a 

 portion of which is well known sometimes to remain in red precipi- 

 tate. 



No directions are given for preparing oxygen gas in the section 

 which treats of its properties. We are merely told that recourse is to 

 be had to the decomposition of its compounds when we wish to pre- 

 pare it ; and in defiance of all propriety, and neglect of all conveni- 

 ence, we are directed to see Manganese, Red Oxide of Lead, Red 

 Oxide of Mercury, and Chlorate of Potassa, — all of which are treated 

 of in the second volume, while the properties of oxygen are described 

 in the first. 



With respect to Hydrogen Gas no advice is given to the young ex- 

 perimenter to allow it to escape for a short time previously to inflam- 

 ing it, or to cover the vessel from which the gas is evolving, in order 

 to prevent the ill effects which might arise from an explosion j and 

 as to the means by which hydrogen gas is obtained, the omissions 

 are, if possible, more glaring than those noticed as to the prepara- 

 tion of oxygen gas. Not only are there no directions given for this 

 purpose, but we are not even told that they are to be found in a sub- 

 sequent part of the work. In one experiment with this gas mention 

 is indeed made of '* a mixture which will furnish hydrogen ;" but as to 

 its composition, no more is said than if it were a profound secret and 

 so intended to remain. It is indeed true that some hints are given 

 as to the preparation of hydrogen gas when Water is treated of, but 

 they are by no means so ample as they ought to have been. 



In the observations prefixed to the section on Acids, Dr. F. remarks, 

 " though Davy considered chlorine and iodine as acidifying principles, 

 yet others maintained that hydrogen is the principle of acidity in those 

 [acids] not containing oxygen. From the arrangement I have adopted, 

 it will be perceived, that if we are really to attach a principle of aci- 

 dity to certain bodies, it should be given to hydrogen, because we find 

 that sulphur, chlorine and iodine, unite with oxygen, and form one 

 set of acids, and with hydrogen to generate another." Now without 

 pretending to feel the force of this reasoning, which we do not under- 

 stand, there are sufficient facts stated in the quotation to induce us 

 to conclude that no acidifying principle whatever exists, especially 

 since oxygen and hydrogen both enter into the composition of several 

 alkalies. Indeed, to admit of the existence either of an acidifying or 

 an alkalifying principle, is in our estimation no more required than 

 to allow of a principle of form or of colour. 



We have neither time nor inclination to present the reader with all 

 the observations which have occurred to us while perusing the section 

 on the Metals. There are, however, some statements respecting a few 

 of them which call for remark, and more especially as to iron and its 

 compounds. Rust of iron is stated by Dr. Fyfe to be a carbonate : 

 but this is not the case $ for no solid compound of carbonic acid and 

 perdxide of iron can be formed, and yet similar assertions occur twice 

 in subsequent parts of this section. "The only compounds of any 



interest 



