318 
POPULAR SCIENCE REVIEW. 
Chromic Acid in Therapeutics. — In the Brdletin General de la Therapeu- 
tique, Ur. E. Magitot recommends chromic acid as an application to various 
allectious of the buccal mucous membrane — such as all forms of stomatitis ; 
and particularly the different kinds of gingivitis, from that connected with 
dentition (as when, for example, it attends the eruption of a wisdom tooth), 
to ulcerative stomatitis. Aphtha3, and divers other ulcerations of the buccal 
mucous membrane, are also, he says, rapidly modified by this agent. But 
the afiection for which he specially recommends the acid is alveolo-dental 
osteo-periostitis.” 
METALLURGY, MINERALOGY, AND MINING. 
The Physical Properties of GadoUnite. — According to the researches of M. 
Des Cloizeaux, the mono-refracting crystals of this mineral (which is named 
after M. Gadolin, a Russian chemist) ought to be referred to the epidote. 
The percentage composition of the Gadolinite from Ytterby is, according to 
Dr. Berlin’s analysis, quoted by the author— Silica, 25-62 ; oxide of yttrium, 
50-00 ; oxide of cerium, T OO; protoxide of iron, 14-44 j lime, 30'00 ; mag- 
nesia, 0-54 ; alumina, 0-48 ; potassa, 019 ; soda, 018. Total, 100-65. — 
Vide Comptes-Rendus, May 10. 
Aluminium a Bell-metal. — Some Belgian manufacturer has just had a bell 
cast of aluminium, and, we [^Scientific Opinion~\ are informed, with very good 
results. It is of course extremely light, so that, though large, it can be 
easily tolled. Its tone is said to be loud, and of excellent pitch. 
The Manufacture of Coppei'as. — The following is a brief statement of 
an improvement in the process for applying copperas to the purification of 
coal-gas, devised by Mr. P. Spence. “ My invention consists in the produc- 
tion of copperas from compounds of iron in a proto state by treatment with 
sulphuric acid. The substance I prefer is the slag of puddling-furnaces, 
commonly called tap cinder, or the slag which results from regulus during 
the process of smelting copper ores, but other proto compounds in a native 
state, or arising from manufactures, may be employed, of the former of 
which I give as examples the Cleveland and blackband ironstones. These 
substances having been ground, are treated in an ordinary manner with 
sulphuric acid in a suitable vessel, and the result is copperas in a dry powdery 
condition, applicable to the purification of gas from ammonia, or to other 
ordinary manufacturing purposes in which copperas is required. If it be 
desired to produce the usual copperas of commerce, it may bo obtained by 
dissolving the dry powdery mass in an ordinary manner, and then cryslal- 
li.sing it, as usually practised in such processes.” — Vide Mining Journal^ 
May 15. 
Utilination of Blast Furnace Slag. — The following method is now adopted 
in several iron works in Belgium : — The slag is allowed to run direct from 
the furnace into pits about eiglit or nine feet in diameter at the top, with 
sides sloping inwards towards the centre, where they are about three feet 
deep. The mass is left for eight or nine days to cool, when a hard, com- 
pact, crj'stalline stone is obtained which is quarried and used for building 
purposes, but chiefly for paving stones. They appear to wear exceedingly 
