208 ANNUAL REPORT 
In the following table their results are arranged: 
Aluminates. 
; Composition. 
Ratio, 
Formula. CaO to 
Al,Os-| a0. |Al,0,. 
Pat test. Ilot test. 
2.0CaOAl.0, 1.10 | 52.38 | 47.62 | Set quick, hard, sound six | Sound; on glass 
weeks. fairly hard. 
2.5CaOAl,O, 1.37 | 57.85 | 42.15 | Set quick, curved and Curved and 
eracked. cracked, soft. 
3.0CaOAl,O, 1.65 | 62.23 | 37.77 | Set quick, curved and Curved and 
cracked. cracked, soft. 
The next question examined was whether the cement formula of 
Chatelier x[ (3CaO)S10,]-+y[ (3CaO) Al,O,] should not be modified to 
x[ (3CaO) SiO,]+y[ (2CaO) Al,O3], since the (3CaO) Al,O; showed such 
inferior qualities. By taking as the clay base, a kaolin and a silicious 
clay base, and using both formulas, it was found that the formula sug- 
gested by Messrs. Newberry produced a much better cement in each case. 
The effect of ferric oxide was also studied, and it was found that a 
mixture of 2CaOFe,O, fused to a black slag which, when ground, was 
brown in color, did not heat nor set in air or cold water. When placed 
in steam it hardened rapidly and did not crack on boiling. 
A mixture of the formula (3CaO)SiO,+ (2CaO)Fe,O;, containing 
7 per cent. of ferric oxide, gave a cement setting slowly and becoming 
hard in 28 days. Sound in hot test and on glass. This shows that 
ferric oxide is able to promote the union of silica and lime similarly to 
alumina. Some mixtures containing both alumina and iron were pre- 
pared in which it was found that perfectly sound and satisfactory cements 
were produced. In one of these cements no lime was assigned to the 
ferric oxide; in the other two molecules of lime were reckoned for each 
molecule of the iron oxide, the percentage of alumina and iron being 4 to 3 
respectively. In another mixture, with 4 and 3 per cent. of alumina and 
iron oxide, but figuring 3 molecules of lime to one of aluimina, the result- 
ing cement showed high tensile strength, but failed in the hot test. The 
alkalies in cement were found to be injurious in effect rather than 
beneficial. 
Magnesium compounds were likewise studied, and it was found 
that when burnt at the highest white heat of the gas furnace the follow- 
ing results were obtained:: 
MgOSi0.,, hard semi-fused clinker, no hydraulic properties. 
(2MgO)Si0O,, well sintered, porous clinker; no cement properties. 
(3MgO)Si0.,, infusible clinker; hardened slowly in moist air, but 
turned to mud on placing in water. 
