M 



UNDULATORY FORCES. LIGHT. 



it WM neceMAry to line powders of a volatile nature 

 which would not clog the wick, and in an unfortunate 

 moi; e of white arsenic. Tin- intro- 



duction of thU deadly poison into candles soon < 

 alarm. f..r they produced very injurious effects on those 

 o vapours of combustion ; and, in fact, it 

 :*coveriea of Clu'vrcul into so grout disre- 

 it almost annihilated tho infant art of stea- 

 rine candle-makim,-. " It is true," say the jurors in 

 :t on tho candles of the Great Exhibition, 

 "this deleterious substance was added in very minute 

 it was entirely incompatible with health, 

 and was soon prohibited on the continent by authority, 

 and in England by equally powerful public opinion." 

 Her. id all the manufacturer's troubles anew. 



In all directions he sought a substitute, and yet found 

 none : at last, after innumerable experiments, and when 

 almost driven to despair, he hit on two simple expe- 

 dients that answered the purpose in the most admirable 

 manner. They were the addition of a very minute 



ruitity of wax to the molted fatty acids, or a! 

 acids to cool almost to the point of congelation before 

 they were poured into the moulds. By this means a 

 sort of liquid pulp is obtained, which sets in the 

 moulds without crystallising. This is the plan adopted 

 at tli lime; the melted acids being constantly 



stirred during their congelation, and the moulds warmed 

 to a temperature of about 110 Fan. before tho semi-fluid 

 mass is poured into tl 



Two, if not three, distinct processes are employed at 

 the present time, for the preparation of the fatty acids. 

 Thf saponification protest is founded on the discoveries 

 made by Chevreul in the year 1823 ; namely, that when 

 fatty matters are boiled with potash, soda, or lime, they 

 are converted into soap by the union of the fatty acids 

 with the alkali ; and that from this soap the acids may 

 be obtained in a more solid condition by the action of a 

 stronger acid, as the sulphuric or hydrochloric. Chevreul 

 saw the importance of his discovery, and took out a 

 ;it for the manufacture of the acids from soaps 

 made with potash or soda. Those, however, wore found 

 to be far too expensive ; and in the year 1831, De Hilly 

 directed attention to the use of lime. 



Tho following is an outline of the process as it is 

 conducted at tho works of the Apollo Company at 

 Vienna ; and of De Milly in Paris, Brussels, and 

 ua. The process is divided into three stages: 

 namely, the saponification of the fat ; the decomposition 

 of the soap by a strong acid ; and the removal of the 

 liquid oil and other impurities by means of pressure. 



(a.) The saponification of the fat is effected by melting 

 the tallow, or the palm oil, in a large vat, by means of 

 steam which issues from a pipe perforated with holes, 

 and then stirring in a quantity of lime in the state of 

 thin cream; ten or fifteen parts of dry lime being 

 used for every 100 of fat. The mixture is kept in 

 a state of ebullition for five or six hours, or until it is 

 completely saponified. It is then allowed to stand, 

 in order that the impurities may settle to the bottom, 

 and the melted soap rise to the surface and cool. The 

 soap thus formed is very hard, and is generally called 

 pock. It is ground to a coarse powder, and is then 

 ready for the next operation 



The decomposition nf the soap by a, strong nn.l. 

 The ground rock-soap is placed in wooden vats lined 

 with lead, and, after being drenched with water, it is 

 raised to a boiling temperature the heat being applied 

 in the same way as before. At this moment the soap is 

 treated with dilute sulphuric acid, using about twenty- 

 five of the strongest acid to every 100 of tallow or palm 

 In this way tho soap is decomposed ; its lime unites 



oil. 



to the acid of the vitriol to form sulphate of lime, or 

 piaster of Paris, which partly dissolves in the water, 

 and settles to the bottom of the vat, while tho fatty 

 acids are set free and float to the surfac-. These are 

 called "yellow matter;" and. after having been well 

 washed with warm water, they are poured off into 

 TweU called "jacks," and from thence into shallow 

 tin pans, where they cool 



(<.) The cakes thus obtained consist of the solid and 

 liquid acids of tho fat; to .Im-h they are 



placed ill horsehair bags, and subjected to hydraulic 

 pressure, gradually : up to about six hundred 



This is extended over a period of six or eight 

 hours, during which the. liquid oleic acid runs out, and 

 carries with it tho brown colouring matter of th< 

 leaving the solid fatty acids in a nearly pure condition. 

 It is generally thought necessary to re-melt the a< 

 and to treat them with a little dilute sulphuric aci.i 

 as to remove iron and other impurities that may have 

 been acquired in the act \ftcr this they 



are a in shallow pans, then placed in 1 



and to a more moderai- of about 



forty tons. During the last operation tho cakes are 

 ly warmed in an atmosphere of steam, so as to 

 ;ito the removal of the last portion of oil. In this 

 way a solid mass is obtained wlu'ch has all the appear- 

 ance of ivory ; and tho product amounts to about thirty 

 per cent, of tho fat originally used. 



The second or vitriolic acid process for obtaining the 

 fatty acids, was originated in 1830, by M. Fremy, who 

 discovered that these acids have tho power of com- 

 bining with concentrated sulphuric acid, to produce 

 compounds which are named sulpho-stcaric, sulpho-oleic, 

 sulpho-margaric, sulpho-palmitic, and sulpho-cocinic 

 These are readily decomposed when they are 

 brought into contact with boiling water, the sulphuric 

 acid being dissolved by the latter, while the fatty acids 

 are set free and float to the surface. This fact was 

 made tho basis of two patents, which appeared in tho 

 yar 1840. One of these was taken out by Mr. George 

 Gwynne, who proposed that the fats should be .separated 

 from tho acids by distillation ; and tho other was ob- 

 tained by Mr. George Clark, who advised that the acids 

 should be set free by simply washing the product. But 

 neither of these patents produced successful results ; 

 and it was not until the year 1844 that the process was 

 so perfected by the labours of Jones, Wilson, and 

 G wynne, as to be applicable to the purposes intended. 

 In that year the names of Wilson and G wynne are found 

 associated in a patent which still continues to be in 

 force. The process adopted by those patentees is now 

 extensively practised at the works of Price's Candle Com- 

 pany, at Vauxhall and Battersca ; and at those of MM. 

 Masse and Tribonillet, at Paris ; of Motard, at Berlin ; 

 of Bert, at Gijon, in Spain ; and at one of the works of 

 the Milly Company at Vienna. 



Tho fats usually employed for this purpose are, palm 

 oil, refuse grease from glue-making and Ixme-boiling 

 and ordinary tallow. The process is as follows : 



1st. The Decomposition of the 1<\ it irilh Sulphuric Add. 

 This is accomplished by first melting the oil or fat in a 

 leaden vessel by the aid of steam, then allowing it to 

 stand for a short time, in order that the mechanical 

 impurities may subside. The liquid fat is now pumped 

 into another vessel, and heated to a temperature of 

 350 Fah. While in this state it is subjected to tho 

 action of strong sulphuric acid using about Gibs, of 

 acid to 11211>8. of palm oil. The acid quickly decom- 

 poses the oil, and gives it a black colour. The latter is 

 now drawn off and transferred to a washing-tank, where 

 it is boiled up with water by means of a jet of steam. 

 After two or three wasliings it is ready for the next 

 operation. 



2nd. The Distillation of t)te Fatty Acids by means of 

 xti;i: rheated Steam. The dark liquid fat of tho washing- 

 tank is conveyed into a copper still, where it is heated to 

 a temperature of 560, and submitted to the action of 

 steam that has been heated to a very high degree by 

 passing through a system of pipes sot in a furnace. The 

 hot steam raises the fatty acids into vapour, and carries 

 them over into a scries of vertical pipes, which act as 

 condensers. These are kept at a temperature of 212; 

 and consequently they retain the fatty acids, but do not 

 arrest the steam. Towards the end of tho process it is 

 necessary to elevate the temperature of the furnace in 

 which tho still is set, and also to raise tho heat of the 

 i, in order that the whole of the fatty matter may be 



