158 



EXTRACTS FROM EXHIBITION LECTURES. 



[1853 



from Upper Asia, and that these hordes and their animals were 

 incorpoi-ated with the original inhabitants, or that the horses were 

 left — and many words ot the language, when the riders had 

 perished or were expelled. Ezekiel seems to allude to such an 

 in\as;on as this when he speaks of a " King of Kings " from the 

 north, with horses, and with chariots and horsemen. "A King 

 of Kings," literally Changan, the name now given by many Tar- 

 tar t] ibes to their chiefs. 



(To be Continued.) 



Extracts fiom Exhibition Lectures. 



Candles. — The manufacture of candles has recently been 

 much im])roved by the aid of Chemistry. Tallow candles, or 

 their more expensive substitute, wax, were generally used till 

 within the last twenty years. The tallow itself was long very 

 impure, containing cellular tissue, which was only partially re- 

 moved in the form of a scum, known as " cracklings." This 

 impurity i-endered the light unsteady, and obstructed the wick. 

 The old method of purification still largely used in this country, 

 thouo-h superseded on the continent and in Dublin, whence such 

 good°Uillow candles were exhibited, has been displaced by a 

 process of treating with _ sulphuric acid the tallow melted by 

 steam. Much of the smell is thus removed, and a larger amount 

 of a purer tallow is obtained. The researches of Chevreul had 

 shown that fats consist of fatty acids, combined with a kind of 

 sugar named glvcerin, which it was important to remove ; this 

 glycerin, remo\ed in candle-making, is now used as liniments in 

 cutaneous atlijctions, and is employed as a remedy in deafness 

 and rheumatism. By boiling with hme, an insoluble soap is 

 formed, \vhile the glycerin remains dissolved in the water. This 

 lime-soap, decomposed by a stronger acid, yields the fatty acids 

 in a purer state. But there arc generally two solid acids mixed 

 with a fluid one; and the latter is easily removed by pressure, the 

 solid fats lemaining. The solid acids are made into the beauti- 

 ful candles erroneously called " stearine," The solid acids, crys- 

 tallizinir rapidly, were ill adapted for candles ; but the introduc- 

 tion of arsenic in small quantity prevented the crystallization. 

 The public were justly alarmed at this dangerous practice, and 

 the manufacture was threatened with extinction, when it was 

 found that a small per-centage of wax produced the same effect, 

 and that large crystals might even be prevented by a careful 

 re"-ulation of the temperature. This evil was therefore avoided ; 

 bu°t a more serious one arose. The ashes of the wicks, becoming 

 heated, cause the fatty acids to splutter ; and this was a gi-ave 

 inconvenience. These ashes, however, form a fusible glass with 

 borax ; so the wicks are dipped into a solution of this salt, and 

 the difficulty removed ; a salt of bismuth is also used for this 

 purpose. Snufi'ei-s, however, are always troublesome, and a self- 

 snutfing candle was an important want. Chemists have told us 

 that fl-mie is hollow, its centre containing no oxygen capable of 

 supporting combustion ; and the wick, being in the hollow part, 

 excluded from the air by its fiery prison, is charred, and dimin- 

 ishes the light. If the wick could be made to turn outwards, it 

 would reach the exterior air and be consumed, whilst the glass 

 formed by the action of the borax on its ;ishes would also be 

 removed. This beantiful scientific fact was attained by the intro- 

 duction of plaited and twisted wicks, the tension of the threads 

 forcing the wick to curl outwards to the exterior of the flame, 

 where it is rapidly burned. 



Another great improvement now took place. In preparing 

 the commercial stearine from palm-oil or tallow, it is essential to 

 remove the glycerin, and this had been accomplished by saponi- 

 fying them with alkalies. Sulphuric acid, acting on fats, unites 

 with the oily acids and with glycerin ; the former compounds 

 are decomposed by water and become insoluble, while the latter, 



from being soluble, is removed ; the oily acids blackened with 

 the destroyed organic impurities, are now distilled, and it is found 

 that a jet of steam, heated somewhat in the manner of the hot 

 blast, aids their distillation, the fatty acids passing over in a 

 comparati\'ely pure form, while the residual black resinous mat- 

 ter is made into black sealing-wax. Candles may now be made 

 from the distilled fatty acids at once, or they may be pressed 

 to remove the oleic acids. 



Tlie oleic acid, both from this mode of manufacture and from 

 that by alkaline saponilicatiou, is principally exported to France, 

 where it is made into a hard soap. In this country we have yet 

 to acquire the method of doing this. The excellence of the acid 

 saponification is, that it is applicable to palm-oil and to the most 

 impure and foetid fats ; by its means the finest candles may be 

 made from the waste of the glue-maker and from the oily resi- 

 dues obtained by the decomposition of the waste lyes of the 

 woollen manufacturer and the bleacher. As the first beautiful 

 process of saponification sprang from the abstract researches of 

 Chevreul, so has the last elegant method arisen from the scienti- 

 fic investigations of Frem}', although both of them have been 

 reduced to practice, with many improvements, by the manufac- 

 turers themselves. The importance of the manufacture may be 

 understood when I state that one company (Price's Candle Com- 

 pany) possesses cocoa-nut plantations in Ceylon, and employs 

 eight hundred workmen in its five manufactories in London, 

 using a capital of nearly half a million, and dividing profits to 

 the extent of £40,000 per annum. 



Chemistry has not yet done so much for the manufacture of 

 wax candles as might ha\-e been anticipated. Wax is still 

 bleached by exjiosure to air and light, and the operation has 

 been hastened more by mechanical than by chemical contriv- 

 ances ; the bleaching of wax is a tedious and often a difficult 

 process, and demands greater atttention from chemists than it 

 has recei\'ed ; the Brazillian mahogany-coloured wax, produced 

 by a black bee hiving under ground, has not yet been bleached 

 by the sun, and might be imijoited in considerable quantity if 

 Chemistry oft'ered means for removing its colour. I do not 

 allude to what Chemistry offers to do; but it would appear that 

 paraffin and oil from coal, and possibly from peat, may dis- 

 pense, to a certain extent, with the necessity for sperm-whale 

 fishing. 



Coal-gas. — The manufacture of coal-gas is an admirable 

 example of the benefits conferred by Chemistry in all the three 

 divisons of its uses ; for it not only economized human power 

 and time, but it has utilized all the products employed in remov- 

 ing its impurities. Coal-gas was onl}' introduced to use at the 

 beginning of this century, and the public prejudice which had 

 to be overcome, and the difficulties to be surmounted in its actual 

 manufacture, may still be remembered by many of my hearers. 

 It was no mean innovation to replace tallow candles and oil 

 lamps by an air streaming through pipes, but the difficulties 

 attending its purification from noxious ingredients appeared 

 even more insuperable thau to reconcile the public to the inno- 

 vation : the gas had an insupportably foetid odour, and certainly 

 injured health when burned ; it discoloured the curtains, tar- 

 nished the metals, eat off the backs of books, and covered 

 everything with its fuming smoke. It required a man of 

 courage, as indomitable as Winsor, its great advocate, to pei-suade 

 the public to continue its use until means were found for the 

 removal of these noxious qualities. Here Chemistry, itself the 

 father of the manufacture, was called in consultation. The inijiu- 

 rities in the gas are sulphuretted hydrogen, which tarnished the 

 metals, and with sulphuret of carbon ]iroduced suli)liureou3 

 fumes ; air.moniacal compounds, which changed the colour of 

 dyes and acted on leather ; tarry vapours, which caused the 

 deposition of »o:>t ; and all these had to be removed. The 



