16S ON ELEMENTARY CHEMISTRY. 
the cyanogen compounds. Another and equally important 
feature, is a short series of test directions, appended to each 
chapter on the metals, to enable the student to distinguish 
them and their compounds from each other. This is a de- 
cided improvement, and supplies a want which is often felt 
in referring to chemical works for that kind of information ; 
for notwithstanding that most of it may be found in the or- 
dinary treatises, yet it is scattered through the text and 
cannot so readily be resorted to. The free use of symbolic 
formulae extends throughout the book, and give an air of 
exactness to all its parts. 
In looking over the list of equivalent numbers of the 
metals, several changes appear, as is the case in Kane's and 
Graham's. The atomic numbers for mercury and gold are 
just one-half of Turner's number, and those for arsenic and 
antimony are doubled. The author observes: " As the 
salts of the red oxide [of mercury] are most stable and per- 
manent, that substance may be regarded as the true prot- 
oxide instead of the grey oxide, to which the term has 
usually been applied. Until, however, the isomorphous 
relations connecting mercury with the other metals shall be 
established, the constitution of the two oxides, and that of 
the corresponding chlorides, iodides, &c.,must remain some- 
what unsettled." 
In the case of antimony, the sesqui-oxide, sesqui-chloride 
and sesqui-sulphuret, become ter-compounds, in which one 
equivalent of the metal is united with three eq. of the other 
elements respectively. Ter-chloride and oxide of gold be- 
come sesqui-chloride and oxide; — and the acid oxides of 
arsenic become ter, and quinto, compounds allied in atomic 
arrangement to the acids of phosphorus. 
However consonant with truth these alterations may be, 
the changes of nomenclature incident thereto are much to 
be regretted in a pharmaceutical sense — as the old chemical 
names for calomel and black oxide will now indicate cor- 
rosive sublimate and red precipitate. 
