July 26, 1888] 



NATURE 



2 93 



various scattered sources, so as to present, in as small a 

 compass as possible, information which it is hoped may 

 be found useful to technological students and others 

 interested in the industries described. Compression of 

 bulk being a main object, it is assumed that the reader 

 has some degree of acquaintance with various points 

 connected with theoretical and practical chemistry and 

 certain analytical processes, so that details in such cases 

 may be omitted without interfering seriously with the 

 usefulness of the book. In carrying out the work of 

 compilation, the same necessity for economizing space 

 has rendered imperative considerable care in selecting 

 and " boiling down " the matter, derived from some two 

 dozen different sources in the way of English biblio- 

 graphy, for the most part published within the last few 

 years ; amongst which may be more particularly men- 

 tioned the works on soap-making, candle-manufacture, 

 and allied industries by Morfit, Kurten, Dussauce, 

 Christiani, Ott, Lant Carpenter, and Watt ; and the 

 Cantor Lectures of Field (" Solid and Liquid Illuminat- 

 ing Agents ") and of Alder Wright ("Toilet Soaps"). 

 References to Continental literature and patents, though 

 comparatively infrequent, are also to be found at intervals 

 throughout the book. 



On the whole, it must be admitted that the author has 

 carried out the work of selection and excision, compila- 

 tion, abstraction, and general editing with great judgment, 

 and that he has succeeded in getting into very small com- 

 pass not only a large amount of general information, but 

 also a valuable epitome of most, if not all, of the various 

 advances in manufacture and the additions to scientific 

 knowledge that have been made up to the present date 

 in connection with the industries treated of, comprising 

 not merely the production of soap and candles, but also 

 the intimately associated manufacture of glycerin. This 

 latter is quite a modern offshoot from the parent indus- 

 tries, neither of which, however, can claim as high an 

 antiquity as some of the metallurgical operations ; for, 

 whilst the property of certain oils and animal fats to 

 become converted into a saponaceous mass by treatment 

 with the lye of wood ashes was known in the first century 

 in an incomplete way, as evidenced by the writings of 

 Pliny, no authentic information is extant leading to the 

 belief that anything of the nature of true soap was known 

 at any much earlier period ; the materials referred to by 

 the Old Testament writers as borith, and translated 

 "soap" (or, in early editions, " sope"), appearing to have 

 been simply alkaline matter, without any oil or fatty in- 

 gredient combined therewith. On the other hand, the 

 manufacture of candles, i.e. a wick surrounded by a solid 

 fusible matter capable of combustion under such circum- 

 stances like oil in a lamp, does not appear to have been 

 practised among the ancients, lamps burning fluid oil 

 being their usual source of artificial illumination : prob- 

 ably torches, or thick wicks impregnated with oil, pitch, 

 &c, and sufficiently stiff to be handled, were the earliest 

 form of candle. Not until the fourth century of our era, 

 however, does this crude device appear to have developed 

 into anything approaching the modern form of candle, wax 

 being then used as the combustible matter in the finer 

 kinds, and tallow or other solid animal fat in the coarser 

 descriptions. 



The researches of the yet living M. Chevreul, made in 

 the early part of the present century, cleared up the 

 chemical constitution of oils and fats generally, and 

 largely helped to bring about great improvements both 

 in the manufacture of soap and in that of candles : they 

 demonstrated that oils and fatty matters in general are, 

 for the most part, compounds analogous to mineral salts, 

 being produced by the union of a " fatty acid " and an 

 organic compound of weak basic character, glycerin, 

 in the same way that a mineral acid and a strong base 

 or metallic oxide will saturate one another to form a salt 

 of the ordinary type ; and that soaps are the alkaline 

 salts of the fatty acids contained in the oil, &c, used, the 

 process of "saponification" being simply the elimination 

 of the organic basic constituent, glycerin, by the more 

 powerful alkali employed, potash usually forming a " soft" 

 soap, and soda a " hard " one. By treating the soaps 

 thus formed with mineral acids, the "fatty acids" are 

 similarly displaced from combination with the alkalies, 

 and substances are thus obtained usually less fusible than 

 the original fatty matter, but, like it, capable of being 

 burnt in conjunction with a wick, and frequently with 

 less liability to smoking and charring the wick. The 

 leading developments of the candle industry thence 

 resulting have accordingly been in the direction of pro- 

 ducing the fatty acids by saponification (or cheaper 

 processes substantially equivalent thereto), and expression 

 of the more fluid constituents (usually, though somewhat 

 unsystematically, termed oleine), so as to render the solid 

 residue, or stearine, of higher melting-point, and therefore 

 better suited to form candles not apt to bend in summer 

 or in hot climates ; and the use of mineral solid hydro- 

 carbons (paraffin-wax and allied materials from paraffin- 

 oil, petroleum, ozokerite, &c.) as ingredients in combina- 

 tion with, and sometimes to the exclusion of, the stearines 

 thus formed. The more solid fats (tallow, suet, and 

 certain solid vegetable fats) are naturally the substances 

 most largely employed, as furnishing the greatest yield 

 of solid stearine suitable for candle-making ; but several 

 oils and semi-fluid products (like palm and cocoa-nut oils), 

 when chilled and pressed, yield a notable quantity of 

 more solid constituents equally available for the purpose. 

 The fluid fatty acids, or " oleines," obtained as by- 

 products in the candle industry, are either neutralized 

 directly by aqueous caustic alkalies, thus forming soaps, 

 or, according to the recent process of Radisson, are fused 

 with caustic alkalies (preferably, but not necessarily, 

 potash), whereby oleic acid becomes converted into solid 

 palmitic acid, of sufficiently high melting-point to be 

 capable of employment for making candles. 



For the manufacture of soaps, scarcely any fatty matter, 

 whatever its source or lack of purity, comes amiss ; it being 

 of course obvious that the coarser kinds are only available 

 for the cheapest scouring soaps, and that only the better 

 kinds can be employed in the production of superior 

 classes of soaps, especially those intended for toilet soaps 

 of high quality (which term by no means applies to all in 

 the market). Recovered greases from wool-scouring and 

 fulling operations, foetid animal fats from the carcasses of 

 horses, bones, and by-products of glue-manufacture and 

 tanning, &c, greasy matters extracted from dead cats and 

 dogs netted in the rivers and streams, and even that 



