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XXVIII. 



ON A METHOD IN QUALITATIVE ANALYSIS FOR DETER- 

 MINING THE PRESENCE OF CERTAIN METALLIC 

 OXIDES. 



By CHAS. R. C. TICHBORNE, F.I.C., Dip. P.H., F.C.S., etc. 



[Read, June 21 ; Received for Publication, Sept. 14; Published, October 31, 1904.] 



The determination of the presence of an oxide either in a mixture 

 or by itself is not always easy ; in fact, it is largely indicated by 

 the negation of special reactions, and by the analyst's knowledge 

 of the special properties of the well-known oxides. 



A recent text-book by an authority on analysis speaks of this 

 question in the following manner 1 : — 



" If no acidulous radical can be detected in a substance under 

 analytical examination, or if the amount found is obviously 

 insufficient to saturate the quantity of basylous radical present, 

 the occurrence of oxides or hydroxides, or both, may be suspected. 

 . , . Hydroxides and oxides insoluble in water not only neutralize 

 much nitric acid, or acetic acid, but are thereby converted into 

 salts soluble in water. Most oxides and hydroxides have a 

 characteristic appearance. In short, some one or more properties 

 of an oxide or hydroxide will generally betray its presence to 

 the student who not only has knowledge respecting chemical 

 substances, but has cultivated the faculties of observation and 

 perception," 



If the above quotation fairly represents the method now in 

 use, it is certainly not very definite. 



To the experienced analyst the ordinary reactions of well- 

 known oxides rarely present a difficulty ; but it is not so with 

 most students, who, lacking a general experience, are often sorely 

 puzzled how to make up their minds on such questions. 



Under these circumstances an easily applied test of a general 

 character is desirable. 



The test I propose is based upon a very simple reaction between 

 the indicator, phenol-phthalein, and the carbonates of sodium. This 

 indicator, phenol-phthalein, as is well known, whilst colourless in 



1 Attfleld's Chemistry, 17th edition, p. 453. 



SCIBNT. PROC. R.D.S., VOL. X., PART II. 2 D 



