601 



CALCIUM. 



CALCIUM. 



602 



turning vegetable yellows brown and blues green. When it is exposed 

 to the air the lime speedily attracts carbonic acid, and pellicle after 

 pellicle of carbonate of lime being formed, the whole of the lime is 

 eventually precipitated : hence the necessity of keeping this solution 

 out of the contact of air. 



M ilk of Lime is merely hydrate of lime diffused through water. It 

 is best prepared by slaking quick-lime with hot water, and adding cold 

 water till the required consistence is obtained. 



Lime is employed for a vast number of purposes in common life, the 

 arts, and manufactures. Among its most important applications are 

 the making of mortar and other cements, and the amelioration of 

 certain soils ; it is extensively used also in soap-making, leather-dressing, 

 dyeing, and for various medicinal purposes. 



Peroxide of Calcium (CaO z ) was discovered by The'nard ; he procured 

 it by the gradual addition of lime-water to peroxide of hydrogen. 

 Small brilliant scales are soon formed, but if much lime-water be 

 added at once then the peroxide of calcium is pulverulent ; it is in the 

 state of hydrate, and decomposes spontaneously, losing its excess of 

 oxygen even when left under water, and also by drying in vacuo. 

 Xeither nitrogen nor hydrogen combines with calcium. 



Chlorine aixl Calcium form one chloride (CaCl). This compound 

 may be formed by direct action, or by passing chlorine gas over lime 

 heated to redness in an earthen tube, oxygen gas is expelled and 

 chloride of calcium remains. It is however more easily procured by 

 saturating hydrochloric acid with lime or chalk, evaporating the solu- 

 tion to dryness, and exposing the residue to a red heat to expel the 

 whole of the water. In this operation the hydrogen of the hydrochloric 

 acid unites with the oxygen of the oxide of calcium ; water is formed 

 and expelled, while the metallic chloride remains. 



If after evaporating the . solution of chloride of calcium to dryness 

 the residue be heated not higher than about 350, a white porous 

 chloride is obtained, containing two equivalents of water. In this state 

 it is well adapted for drying gases. 



The properties of chloride of calcium (formerly called muriate of 

 lime) are : It is colourless, possesses a crystalline appearance when 

 broken, is inodorous, and has an extremely bitter saline taste. It 

 is very deliquescent, and on account of this property it is frequently 

 employed in chemical researches to separate water from gases in order 

 to render them dry, and also to combine with this fluid and with alcohol 

 in various other cases. It fuses readily by heat. Chloride of calcium, 

 after being heated, shines in the dark, and was formerly called Hom- 

 berg's phosphorus. 



When a concentrated aqueous solution of this salt is suffered to cool, 

 crystals are deposited, which, like the anhydrous chloride, are extremely 

 deliquescent. They consist of 



1 Equivalent of chloride of calcium = 55-5 

 6 water . . . = 54'0 



Equivalent = 109-5 



These crystals are remarkable for the great degree of cold which 

 they occasion when mixed with snow ; but the anhydrous chloride dis- 

 solves in water with the extrication of heat. The crystals are soluble 

 in one-fourth their weight of water at 60. The amount of chloride of 

 calcium present in an aqueous solution is most conveniently determined 

 by the specific gravity of the liquid. Thus : 



8p. ST. 

 1-46 

 1-42 

 1-39 

 1-86 

 1-33 

 1-80 

 1-27 

 1-24 



Per cent. 

 41-91 

 40-43 

 3831 

 36-49 

 34-57 

 82-35 

 29-67 

 16-M 



Sp. gr. 

 1-21 

 1-18 

 115 

 1-12 

 1-09 

 1-06 

 1-03 



Per cent. 



23-93 



20-85 



17-60 



14-42 



11-23 



7-66 



3-95 



Bromide of calcium (CaBr) is obtained by dissolving chalk in hydro- 

 bromic acid. It is a colourless, bitter, deliquescent substance, which 

 readily dissolves hi water, with the evolution of heat. The aqueous 

 solution does not easily yield crystals ; they contain much water. 

 Sromattoflime (CaO r Br0 5 ) is prepared by saturating bromic acid 

 with lime or its carbonate. 



Iodide of ralcium (Cal). Best made by decomposing sulphide of 

 calcium with iodine, filtering, evaporating to dryness, and heating out 

 of contact of air. The resulting flaky mass has a pearly lustre. It 

 may be easily powdered. 



Iodide of calcium is soluble In water, a hot solution yielding long 

 needles of hydrated salt. 



lodate of lime (CaO, 10,), a crystalline compound obtained by double 

 decomposition of iodate of potash and chloride of calcium. 



Carbon and calcium form no compound. 



flulfihur and calcium may be made to unite in three proportions. 

 The sulphide, or proto-sulphide(CaS),is obtained by mixing anhydrous 

 sulphate of lime with one-fifth of its weight of powdered charcoal, and 

 heating the mixture to whiteness for two hours in a covered crucible. 

 It is a reddish-whito compound, which is but slightly soluble in water, 

 and suffers but little change even when long kept in it. The aqueous 



solution is colourless, and has an alkaline and hepatic taste ; when 

 evaporated in vacuo, white crystals of the sulphide are formed. When 

 acted upon by hydrochloric acid, sulphuretted hydrogen gas is evolved. 

 After exposure to light, this sulphide shines in the dark, and has been 

 called Canton's phosphorus. 



Bisulphide of calcium (CaS 2 ) is obtained by boiling, but not to 

 saturation, hydrate of lime and sulphur in a large quantity of water. 

 On cooling, yellow needle-shaped crystals are obtained, which are soluble 

 in 400 times their weight of water at 60, but more so in boiling water, 

 and contain about 43'5 per cent, of water. When lime and sulphur 

 are boiled together in water, till sulphur ceases to be taken up, per- 

 sitlfhide or pcntamlphidc of calcium is formed, consisting of 



1 Equivalent of calcium = 20 

 6 sulphur = 80 



Equivalent = 100 



Phosphorus and calcium constitute the phosphide (Ca 2 P), and like all 

 the binary compounds of this metal hitherto described, except the 

 oxide, it is entirely an artificial product. It is prepared by heating lime 

 in a crucible, and passing vapour of phosphorus into it : 



P, + HCaO = 2(2CaO, POJ + 5C 2 P. 



The mixture of phosphate of lime and phosphide of calcium procured 

 is of a brown-red colour. 



This phosphide readily decomposes water, and phosphuretted hydro- 

 gen gas is evolved ; when dissolved in hydrochloric acid this gas is 

 abundantly procured. 



Selenium and calcium may be combined by exposing a mixture of 

 selenium and lime to a heat a little below redness. The resulting 

 impure selenide is a brownish-black substance, which has neither emell 

 nor taste, and is insoluble in water ; when heated to redness it loses 

 selenium, and selenide of calcium remains. Crystals of this substance 

 may be formed by preparing a solution of lime in hydroselenic acid and 

 exposing it to the air. It is composed of 



1 Equivalent of calcium = 20-00 

 1 selenium = 39'62 



59-62 



No compound of boron and calcium is known. 



Fluorine and calcium occur largely in nature, in combination, and 

 form fluoride of calcium (CaF, Equiv. 39), called by mineralogists fluor 

 spar. [FLUOR SPAR.] 



Cyaiioyen and calcium form a cyanide which has been but slightly 

 examined ; it is obtained by saturating hydrocyanic acid with hydrate 

 of lime. It exists only in solution ; by evaporation it is converted 

 into formate of lime and ammonia. 



Oxy-acidt and lime combine to form a numerous class of salts ; of 

 these, the most important only are here described. Two of them 

 namely, the carbonate and sulphate occur in great plenty in almost 

 every part of the earth ; the phosphate is more rarely met with. 



Nitric acid and lime very readily combine and yield nitrate of lime 

 (CaO, N0 5 ). It may be formed either by adding lime or chalk to 

 nitric acid. A colourless solution is obtained, which is extremely 

 bitter, and by evaporation long prismatic crystals are formed (CaO, 

 NO S + 4Aq.) ; like the anhydrous salt, they are extremely deliquescent. 

 These crystals dissolve in one-fourth of their weight of cold water, and 

 in all proportions in boiling water ; they are also very soluble in alcohol. 

 Nitrate of lime is readily decomposed by heat ; the residue gives a 

 feeble light in the dark, and has been called Baldwin ' phosphorus ; it 

 is stated to be composed of nitric oxide, nitrous acid, and lime, but 

 when the heat is very long continued then pure lime is obtained. 

 Nitrate of lime is often found in considerable quantity in spring water. 

 It is applied to no use. 



Carbonic acid and lime form carbonate of lime. [CALCAREOUS SPAR.] 



Carbonate of lime (CaO, C0 2 ) constitutes the greater part of all 

 shells, and enters into the composition of bones. Like sulphate of 

 lime, it is found in most spring waters, held in solution by an excess of 

 carbonic acid, and to this in part the hardness of water is owing. 



By boiling water containing carbonate of lime dissolved in carbonic 

 acid, the latter is expelled and the former precipitated. Such water 

 will of course be softer than in its original condition, and hence carbo- 

 nate of lime is said to produce temporary hardness, while sulphate of 

 lime, not being affected by ebullition, gives permanent hardness to water. 

 Both salts are decomposed by soap, which forms the familiar, insoluble, 

 curdy precipitate (margarate and itearate of lime), and it is not until 

 all the lime is removed in this way that a permanent lather can be 

 obtained. Moreover, in using hard water for domestic purposes, that 

 portion of the insoluble lime-soap precipitated in the pores of the skin, 

 or in the fibre of fabrics submitted to cleansing operations, carries 

 down with it, like the mordant in the process of dyeing, a portion of 

 the colouring matter, the removal of which is the object of the ope- 

 rator. For these reasons, carbonate and sulphate of lime may be 

 considered as impurities in water ; at the same time, it must be borne 

 in mind, that a certain quantity of these and other salts probably pre- 

 vent lead from being dissolved from pipes through which the water 



