: STATE GEOLOGIST. 39 
produce a very hard cement by burning talc at a very high temperature. 
Lieven also claims to have produced well hardening cements by igniting 
a mixture of one equivalent silica with one equivalent of magnesia. Rivot* 
says that magnesium silicates behave similarly to the lime compounds, 
while Held was not able to produce any hydraulic compounds from mag- 
nesia minerals and artifically prepared silicates. XKawalewsky again 
reports on vitrified magnesia cements which after ten years were still 
found to be sound and which had shown high tensile strengths. Zulkow- 
ski prepared the dimagnesium silicate and found it to show hydraulic 
properties, setting in two hours to a hard, earthy mass. After two months 
in water it attained moderate hardness. 
**S. B. and W. B. Newberry came to the conclusion that magnesia 
shows no hydraulic properties when heated with silica, alumina or clay, 
and says that it probably plays no part in the cement reaction. Hence 
these investigators claim that magnesia cannot replace lime in cement 
mixtures. 
Sorel Reaction.—Magnesium oxide burnt at a low temperature, mixed 
with solutions of salts, like magnesium chloride or calcium chloride, 
produces extremely hard though usually slow-setting cements, used to 
some extent in fastening brass to glass as in lamps, laying floor or wall 
tiles, or similar purposes. Cements of this type are called Sorel cements 
and include also similar mixtures, like calcium oxide and calcium 
sulphate, anhydrous gypsum made up with a solution containing Glauber’s 
salt or potassium sulphate and others. The last named mixture even is 
hydraulic in character and is extensively used for making floors in place 
of Portland cement being known as Estrich or Mack’s Cement. The 
Sorel reaction depends on the formation of basic double salts, as a rule 
very insoluble in character. Kosmanny7 attributes the formation of these 
compounds to the so-called chemica! residual energy. Though the chem- 
ical valency of many compounds is satisfied they have not yet lost all 
chemical activity, in fact, many of the so-called neutral salts may be 
considered as unsatisfied compounds. This seems to be shown by their 
thermo-chemical behavior. It is found that outside of the heat produced 
by the combination of acids and bases there is still some heat left which 
represents a certain chemical energy. This heat is called by investigators 
the residual chemical energy which enables the so-called neutral salts to 
take up water in chemical combination as well as to add, in place of water, 
salts or oxides to the molecular structure. All of the salts of strong acids 
and bases are caustic in nature, which is shown by their tendency to take 
water from other salts. Examples of this kind are cupric sulphate, lead 
chloride, cupric chloride, sodium carbonate and many others. This caus- 
*Wagner’s Jahresbericht, 1856, p. 181 
**The Constitution of Hydraulic Cements. Journal Society Chem. Industry, Nov. 189%. 
+Transactions, Deutscher Verein fuer Ton, Cement und Kalk-Industrie, 1900. 
