MANUFACTURE OF CEMENT.

Waikato Times, Volume XVIII, Issue 1484, 7 January 1882, Page 4

MANUFACTURE OF CEMENT.

In connection with the various projects which t are at the present time being put forward, those having reference to the local manufacture of cement are of special importance to this colony. Of the requisite materials we possess a practically unlimited supply ; ami even the produc tion of so much cement as is used in New Zealand would he an undertaking of considerable magnitude. Some interesting details of tlie natural and artificial cements in übe have recently been compiled in a condensed form, as follows :—: — Certain limestones, which contain upwards of 10 per cent, silica, possess the property, when burned, of forming a cement or tuortar which hardens under ■water. Some limestone is called hydraulic lime, and the mortar is called hydraulic mortar. Tin's stone, before burning, consists of a mixture of carbonate of lime and silica, or a silicate, chiefly silicate of alumina. The latter is insoluble in hydrochloric acid, hence remains unclissolved when the stone is treated with this acid, but in burning this silicate is fluxed by the alkaline caibonates and becomes soluble in acid, the carbonic acid being expelled. When common lime is slaked it swells enormously and developes a great deal of heat ; this is not the case in slacking hydraulic lime, which absorbs water without any considerable increase of temperature or volume. If ordinary lime be mixed with a suitable quantity silica or sand, an aitifici.il hydraulic mortar is obtained, to which we apply the name of cement. These cements may be either natural or artificial. The former are found in volcanic regions, having been produced by the terrestrial heat. Puzzuolana, found at Piuzuoli, near Naples, is a natural cement of the following composition : Silica,, 4i"5 ; alumina, 15 0; lime, 8"8 ; magnesia, 47 ; oxide of iron, 12"0 (with oxide of titanium) : potash and soda, 5-5 ; water, 93 ; total, 100.8. The quantity of lime is., however, so small that it requires to be mixed with ordinary lime to form hydraulic mortar. It was employed in combination with an equal quantity of lime in building the Eddystone Lighthouse. Artificial cement, also called "Roman cement" because it is not made in Rome, has been manufactured in England, on the Thames, and in the isles ot Wight and Sheppcy since 1796. It is made by burning the calcaieous nodules which oveilie the chalk in that countzy. A sample analysed by Micluielis contained : lime, SS'3S ; magnesia, 5 ; silica, 28*83 ; alumina, (5 40 ; oxide iion, 4"SO. When mixed with water it hardens in fifti en minutes, and possesses great firmness and stiength. Poitkml cement was patented in Kngland by Jo-cpli Aspdin m 1824. He took the limestone of Leeds, pul\ciised find burned it, then mixed it with watei and an equal weight of clay to a plastic mass. When diy this was broken up and burned again until the eaiboinc acid was all expelled. It was then pul\ erised and was ready for use. Tasluy made it fiom chalk or limestone with Medway River clay, which contains salt-. Pettenkofer suggests that content is inipiovcd by soaking the clay in salt ■water. Portland cement ib now made, says Wagner, by making blicks of an intimate mixture of limestone and clay, diying them in the air, and burning them in a tall shaft furnace from 43 to 100 feet, 12 feet in diameter, with a strong quite 4 feet from the bottom. It is charged m ith alternate layers of co 1 and cement stone. The propel tics of the cement are largely dependent on the tempeiatnic employed in buring ; a white heat is best, but if the temperature is too high it will no longer unite with watei, and may even be melted to a glass. If the tomperatiue does not exceed a red heat it unites readily with water and gets hot, like ordinary lime, but possesses very little strength. The colour changes with the binning, and forms a ciiterion for judging the quality. In its normal condition it fonm a giay, shaip, powder, with a shade of gicon, but not glassy. The lnanufactui c of Portland cement is now carried on in every part of the world where limestone mid clay arc to bo found. In oidcr to obtain a good cement, not only must the proper heat be employed in burning, but the proper proportion of clay, usually 25 per cent, must be used, and the clay must have certain properties, such as a large proportion of silica, must be very finely divided, and must be very intimately mixed with the limestone. Amilyoes of Portland cement from various soiuoos show the percentage of lime to vary from 53 to 02 ; silica, 23 to 25 ; alumina, sto (i ; oxide of iron, 2 to 6 ; soda and potash, usually less than 1 per cent.

Count no gaulen complete without a wide hedge of sweet peas, for there are no cut flowers for vases and bouquets) that sin pass them in beauty and fragrance A vase of sweet peas, mingled ■with bjn.iys of the blue forget-me not and clusters of the misty gypsophila, is always exquisite, whether for table or jwrlour decoration. I have seen a hedge of sweet peas 120 feet long planted this year, v Inch I) 3' the middle of June will iill the air with its most delicious fiagiance, and will continue in beauty until the frost destroys it. — American paper. I ha\ i; many times given one of the best and most effectual remedies for killing lice which I have ever used, and many other persons who have used it on cattle, calves, horse, and dogs. The remedy is quite fiec fiom danger, and can be applied at any time in waim or moderate m eather. Mix thoroughly two drains of arsenious acid (arsenic) with a lull quart of soft water. With a small piece of sponge or rag rub well into the parts infested by the lice. Keep constantly shaking or stiring the mixture, as the poison will not dissolve in water, but will sink to the bottom quite rapidly, as it is heavy — Win. Homo, Y.S., in Country Grentleman. TnE plan described below for preserving butter is a very old one, and it enjoys tho reputation of being good : — To three gallons of brine strong enough to bear an egar, add a quarter of a pound of fina white sugar, and one tablesooonful of saltpetre. Boil the brine, and when it is cold strain carefully. Make your butter into roll', and wrap each separately in a clean white muslin cloth, tying up with a string. Pack a large jarful, weight the butter down, and pour over it the brine until it is all submerged. This will keep really good butter perfectly sweet and f ret-h for a whole year. Be cai eful not to put ice upon the butter you wish to keep for any length of time. In summer, when the heat will not admit of small jars, tvMe large ones, and, using tho same brino allow it to cover th^ butter to the depth of at least four inches. This excludes the air, and answers as well a,B the first method suggos ted. Thk largest of the salivary glands is situated in a curved line from the jaw to the ear, and when inflamed from any o'luse a swelliug ocouis on the jaw -or cheek and throat up to the ear. When this happens tho swelling should be bathed vith waim water and then rubbed with iodine ointment in the effort to disperse the swelling or causs it to suppurate or break. Give an ounce of hyposulphite of t-oda daily while- the swell ng last-". It will probably continue for ,a week or ten days and then disappear/ gradually or break and discharge. ' * ~ ""•' " "