CHEMICAL SCIENCE. 223 



base, which is not attacked by acids, is infusible, and has all the properties 

 of kvanite. It is interesting to observe that in this reaction chloride of alu- 



. o 



minum is produced at the cost of the silicium. 



In order to produce a double silicate, it is not enough to mix with two 

 bases in the requisite quantity, but there must be an excess of one of them in 

 order to supply the requisite amount of oxygen to the silicon. In this way a 

 mixture of lime and magnesia yields colorless and transparent crystals of 

 augite (diopside). By a mixture of seven equivalents of potash or soda, and 

 one of alumina, or one of alkali, one of alumina, and six of lime, crystals of the 

 form and characters of feldspar are obtained. By using different bases, and 

 modifying their proportions, crystallized Willernite (silicate of zinc), idocrase, 

 garnet, phenakite. emerald, euclase, and zircon are obtained. By making a 

 mixture corresponding to the constituents of magnesia, tourmaline and iron, 

 and magnesia tourmaline, adding excess of lime or magnesia, and exposing 

 the whole to the chloride of silicium, in addition to rock crystal, very distinct 

 hexagonal prisms with all the properties of tourmaline were obtained. By 

 passing chloride of aluminum over red-hot lime, crystals of alumina, corre- 

 sponding to the two well-known forms of corundums, w^ere obtained. "When 

 magnesia is used, the silicic acid unites with the excess, and crystals of spin- 

 elle are produced. A mixture of chloride of zinc and aluminum, brought in 

 contact with lime, produces gahnite. Chloride of titanium, acting on lime, 

 produces titanic acid in the form of Brookite. Chloride of tin gives the crys- 

 tallized oxyd. Chloride of iron gives specular iron ore, and if mixed with 

 chloride of zinc, Franklinite is produced. Chloride of magnesium gives crys- 

 tallized magnesia, exactly similar to the periclase of Monte Somma. 



The result of these experiments lead to many interesting conclusions. They 

 show us how such minerals as augite, garnet, epidote, axinite, and many 

 others, which certainly can not have been produced by fusion, may be formed. 

 Indeed, the production of a large number of minerals may. with great proba- 

 bility, be attributed to the action of volatile chlorides and fluorides, and the 

 penetration of those into the fissures of limestone ; and the very powerful ac- 

 tion of lime on these compounds may explain the abundance of silicates which 

 exist disseminated through many limestones. Minerals, such as spinelle, 

 chondrodite, mica, augite. amphibole. serpentine, etc., are frequently found in 

 limestones which contain no magnesia^ and this hitherto unexplained fact may 

 be due to the difference in the chemical affinities of lime and magnesia ; for it 

 is observable that in all these experiments chloride of magnesium is decom- 

 posed by them. Many other obscure facts may also be explained by reference 

 to these researches, which are of very great mineralogical interest. JI. Daur 

 bree. Comptes Rendus, v. xxxix, p. -135. 



OX THE ELECTROCHEMICAL EXTRACTION OF METALS FROM 



THE HUMAX ORGANISM. 



During the past year great success has attended the workings of a plan de- 

 vised by M.M. Tergnes and Poey, for extracting metallic compounds from 

 the human system by means of chemico-electricity. The arrangement of the 



