STATE GEOLOGIST. 215 
B. Steuer* allowed hydrogen sulphide to act upon water in which 
finely powdered Portland cement had been poured. In this manner he 
extracted 44 per cent. of calcium oxide which he considered free lime, 
while the residue corresponded to the formula CaOSiO,,. 
S. Wormser and O. Spanjer* used as reagent for the solution of 
free lime an alcoholic solution of aluminum chloride. They claimed to 
have proven that this solution (1 g. in 100 cc, absolute alcohol) does not 
decompose the silicates, but dissolves only free lime. ‘The per cent. of 
CaO found to go in solution as such was 25, while in addition 20 per cent. 
of lime was found present as a highly basic silicate. They calculated, by 
means of their method, a content of 26.6 per cent. of free lime, and 18.65 
per cent. of CaO, combined with 6.15 per cent. silica. 
Dr. Hart* in the same year, by means of a 10 per cent. alcoholic 
iodine solution, found, he claims, 30.34 per cent. of free vitrified calcium 
oxide in Portland cement; the balance of the cement material he con- 
siders as ballast, as slag which does not harden; on hydrating, this vitrified 
lime hardens under water. He cites this free lime as a fine example of a - 
body whose chemical energy is manifested, not by a thermal reaction, but 
by a mechanical development of energy. The reason why so much free 
calcium oxide is not injurious to the cement, he explains by saying that 
this lime is vitrified and crystalline. Vitrified, crystalline calcium oxide 
and the amorphous lime, though not distinguished analytically, are dif- 
ferent physically. This argument is open to many objections, whose 
discussion here would lead too far. 
HEAT REACTIONS. 
Dr. Hart’s work was ‘supplemented, however, by thermo-chemical 
experiments, in which he determined the heats of neutralization of wol- 
lastomitesCa@s1©-sartiticialsCa®si@,. 2Ca®@si@>,2€a©si©,, CaOAl ©: 
2CaOAl,O,, 3CaOAl,O,. He determined the heats evolved for the an- 
hydrous cement as well as for the hydrated and dehydrated cement which 
had been allowed to harden. The heat of neutralization of the hardened, 
not dehydrated cement should be higher than that of the clinker, since the 
former contains a considerable amount of free calcitum hydrate. In 
Portland cement the heat of neutralization is lowered on hydration, while 
the heat evolved by the dehydrated cement is almost equal to that of the 
clinker. From this Dr. Hart concludes that from 30 to 34 per cent. of 
free lime must be present in cement. 
3 Tbid, 1899, p. 604. 
4 Ibid, p. 1785. 
*Tonindustrie Zig. pages 659, 770, 853, 1899; 1900, p. 188. 
