Fernan Gomez followed in 1469, and opened trade with the Gold Coast; and in 1484 Diogo Cao discovered the mouth of the Congo.
Thus if we wish to ascertain the thermal effect of the action Mg+CaO =MgO+Ca, we may write, knowing the heats of formation of CaO and Mg0 to be 131000 and 146000 respectively, 0-131000 = 0-146000+x x =15000 cal.
A good quality of sheet-glass should show, on analysis, a composition approximating to the following: silica (SiO 2), 72%; lime (CaO), 13%; soda (Na 2 O), 14%; and iron and alumina (Fe 2 O 3, Al 2 O 3), 1%.
The following is a typical analysis of high quality bottle-glass: S102, 69.15%; Na 2 0, 13.00%; CaO, 15.00%; Al 2 0 3, 2.20%; and Fe 2 0 3, 0.65%.
The following is an analysis of a specimen of English pressed glass; S102, 70.68%; Na 2 0, 18.38%; CaO, 5.45%; BaO, 4.17%; Al 2 0 3, 0.33%; and Fe203, o.
CaC2 -}- H 2 O = C 2 H 2 -}- CaO Lime.
CaO -IH20 = Ca(HO)2.
It combines directly with most elements, including nitrogen; this can be taken advantage of in forming almost a perfect vacuum, the oxygen combining to form the oxide, CaO, and the nitrogen to form the nitride, Ca 3 N 2.
Calcium forms two oxides - the monoxide, CaO, and the dioxide, CaO 2.
The dioxide was obtained as the hydrate, CaO 2.8H,0, by P. Thenard (Ann.
An oxysulphide, 2CaS CaO, is sometimes present in "soda - waste," and orangecoloured, acicular crystals of 4CaS CaSO 4.18H 2 O occasionally settle out on the long standing of oxidized "sodaor alkali-waste" (see Alkali Manufacture).
The element is not found in the free state in nature, nor to any large extent in combination, occurring chiefly as chrome-ironstone, Cr 2 O 3 FeO, and occasionally being found as crocoisite, PbCrO 4, chrome-ochre, Cr 2 0 3, and chromegarnet, CaO Cr 2 O 3.3SiO 2, while it is also the cause of the colour in serpentine, chrome-mica and the emerald.
Compounds embraced by the second definition are more usually termed hydroxides, since at one time they were regarded as combinations of an oxide with water, for example, calcium oxide or lime when slaked with water yielded calcium hydroxide, written formerly as CaO H 2 O.
This lime is charged in the form of common quicklime, CaO, resulting from the calcination of a pure limestone, CaCO 3, which should be as free as possible from silica.
The river Congo was discovered by Diogo Cam or Cao in 1482.
(1481-1495) the fortress of Sao Jorge da Mina, the modern Elmina, was founded for the protection of the Guinea trade in 1481-1482; Diogo Cam, or Cao, discovered the Congo in 1482 and reached Cape Cross in 1486; Bartholomeu Diaz doubled the Cape of Good Hope in 1488, thus proving that the Indian Ocean was accessible by sea.