754 CEMENTS 



Celestine occurs in fine crystals, associated with sulphur and gypsum, at Girgonti 

 in Sicily ; and is also found under like circumstances at Conil in Spain. With rock- 

 salt and gypsum, it is found at Bex in Switzerland, and at Ischl in the Salzkammergut. 

 It occurs abundantly, also with gypsum, in the New Red marls in the neighbourhood 

 of Bristol ; it is found in nummulitic limestone (Eocene) at Mokattam, near Cairo ; and 

 in Trenton limestone (Lower Silurian), at Strontian Island and elsewhere on Lake 

 Huron. It is recorded from the eruptive rocks of Calton Hill, Edinburgh; and 

 from the neighbourhood of Tantellan in the East Lothians. It is found in chalk- 

 flints at Meudon near Paris ; and in the gypsum-quarries of Montmartre. Fine fibrous 

 masses of blue celestine come from the neighbourhood of Jena. 



Celestine is decomposed by ignition with charcoal into sulphide of strontium, which 

 is converted into the nitrate by the action of nitric acid. The nitrate of strontia is 

 employed for the production of the red light in theatrical fireworks. 



CEXADXAR BEAM. An application of wrought iron, in which wrought iron 

 plates are rivetted with angle irons in the form of longitudinal cells with occasional 

 cross struts. Fairbairn on Cast and Wrought Iron. 



CEXiIiirx.oSE. The essential part of the solid framework of plants. See Watts's 

 ' Dictionary of Chemistry.' 



CEMENTATION. A chemical process, which consists in imbedding a solid body 

 in a pulverulent matter, and exposing both to ignition in an earthen or metallic case. 

 In this way, iron is cemented with charcoal to form steel, and bottle glass with gypsum- 

 powder, or with sand, to form Reaumur's porcelain. 



CEMENT COPPER. The precipitate of metallic copper, formed by the action 

 of iron on a solution of a salt of copper, is called Cement Copper. In like manner, the 

 silver precipitated from a solution of a silver salt by metallic copper is known as 

 Cement Silver. 



CEMENTS. (Ciments, Fr. ; Cdmente, Kitte, Ger.) Substances which are capable 

 of assuming the liquid form and of being applied between the surfaces of bodies so as 

 to unite them firmly when solidifying. They are of very varied character. 



Gum, glue, and paste are cements, the uses of which are well known. 



Diamond cement is a preparation of isinglass and gum ammoniacum dissolved in 

 alcohol (see AMMONIACUM GUM) : it is employed to mend glass and china. 



Sir John Robinson's cement he thus describes : 



' If it be wished to dissolve good isinglass in spirits of wine, it should first be 

 allowed to soak for soma time in cold water, when swelled it is put into the 

 spirit, and the bottle containing it being set in a pan of cold water may be brought 

 to the boiling point, when the isinglass will melt into a uniform jelly, without lumps 

 or strings, which it is apt to have if not swelled in cold water previously to being put 

 into spirits. A small addition of any essential oil diminishes its tendency to become 

 mouldy. 



' If gelatine, which has been swelled in cold water, be immersed in linseed oil and 

 heated it dissolves, and forms a glue of remarkable tenacity, which, when once dry, 

 perfectly resists damp, and two pieces of wood joined by it wilJ separate anywhere 

 else rather than at the joint. Ordinary glue may bo thus dissolved, and sometimes a 

 small quantity of red lead in powder is added." 



Shellac dissolved in alcohol, or in a solution of borax, or still better in naphtha, 

 forms a good cement. White-of-egg alone, or mixed with finely sifted quick- 

 lime, will answer for uniting objects which are not exposed to moisture. The latter 

 combination is very strong, and is much employed for joining pieces of spar and 

 marble ornaments. A similar composition is used by coppersmiths to secure the 

 edges and rivets of boilers ; only bullocks' blood is the albuminous matter used in- 

 stead of white-of-egg. Another cement in which an analogous substance, the curd 

 or caseum of milk is employed, is made by boiling slices of skim-milk cheeses into 

 a gluey consistence in a great quantity of water, and then incorporating the mixture 

 with quicklime on a slab with a muller, or in a marble mortar. When this com- 

 pound is applied warm to broken edges of stoneware, it unites them very firmly after 

 it is cold. 



A cement which gradually indurates to a stony consistence may be made by mixing 

 20 parts of clean river sand, 2 of litharge, and 1 of quicklime, into a thin putty with 

 linseed oil. When this cement is applied to mend broken pieces of stone, as steps of 

 stairs, it acquires after some time a stony hardness. A similar composition has been 

 applied to coat over brick walls, under the name of ' Mastic.' Portland oolite powder 

 with a little litharge and oil makes good mastic. 



The iron-rust cement is made of from 50 to 100 parts of iron borings, pounded 

 and sifted, mixed with one part of sal-ammoniac, and when it is to be applied 

 moistened with as much water as will give it a pasty consistency. Formerly flowers 

 of sulphur were used, and much more sal-ammoniac, in making this cement, but with 





