REVIEWS. 
351 
"before us brings the record of Chemical Discovery down to the end of the 
year 1879, including the more important discoveries which appeared in 
1879 and 1880. Among the important articles in this final portion of the 
eighth volume are those on Gallium, Gases, Glycerine, Gold, Granite, 
Guano, Gypsum, Heat, Hornblende, Hydrocarbons, Iodine, Iron, Isomerism, 
Lead, Light, Magnetism, Manganese, Mercury and Mercury Compounds, 
Meteorites, Methyl and Methyl Derivatives, Mica, Milk, Molybdenum, Napth- 
lenes, Nicotine, Nitrifications, Nitrates, Oils, Olivine, Organic Compounds, 
Paraffin, Petroleum, Phenol, Phosphorus, Phosphates, Platinum, Pyroxene, 
Pesin, Selenium, Serpentine, Silver, Soda, Spectral Analysis, Starch, Sugars, 
Sulphides, Sulphur, Sulphuric Acid and Sulphates, Tellurium, Thermodyna- 
mics, Tin, Titanium, Toluenes, Trachyte, Tungsten, Vanadium, Vapour- 
Density, Volcanic Products, Yttrium Metals and Zeolites. 
Chemical research has been unusually active during the eighteen years 
this Dictionary was in course of preparation, and has resulted in such a 
mass of facts that in order to record them fairly it has been necessary to 
extend the work to over ten thousand five hundred closely printed octavo 
pages. 
The time which has elapsed since the appearance of the first volume has 
also necessitated the addition of various comprehensive] supplements, since, 
in order to bring down the information to date, three or more successive 
articles on the same subject have sometimes been required. In no case, 
however, has the same matter been reprinted, and consequently by taking 
the various articles in the order of their sequence, the student has laid before 
him a continuous history of the subject under consideration. 
Dr. Watts has performed his task with great care and industry, and has 
produced a work, which, furnishing, as it does, a complete epitome of the 
science of which it treats, should be accessible to every advanced student of 
chemistry. This work is not, however, entirely free from slight blemishes, 
among which may sometimes be observed evidences of careful compilation 
rather than of the exercise of an intelligent discrimination with regard 
to the relative values of the different processes described. 
As an example of this want of appreciation, attention may be 
directed to the article Silver, in which we are told that two methods are 
employed for the removal of that metal from solutions obtained by the lixi- 
viation of burnt cupreous iron pyrites, namely, Claudet’s process, which 
depends on the almost complete insolubility of iodide of silver in solutions 
of metallic and alkaline chlorides, and Gibbs’, which consists of blowing 
through the copper liquors a mixture of air and sulphuretted hydrogen, 
when the first precipitate obtained contains a larger proportion of silver than 
that subsequently produced. The cost and the production of the two pro- 
cesses are represented as being the same, and the student will naturally 
infer that they are equally valuable. 
As a matter of fact, however, Claudet’s process is, without exception, 
universally employed, while the other, although experimentally tried for a 
short time, was found commercially unsuccessful. Such occasional inaccu- 
racies will doubtless be corrected in a second edition. 
