•':' SOME CURRENT PROBLEMS IN ,. countered in pressing and stamping. ß (a) The employment of a base ed of highly unsaturated acids is to be avoided, owing , the likelihood of rancidity develop- with consequent discoloration //nd spotting after exposure to the Impurities contained in certain and fatty acids are frequently that have a detrimental effect stability, and a prior "cleaning process saves much later trouble, as colour development, odour :terioration, etc. Another inter- point is that taJlow obtained animals that have been fed :•!i} oil cakes and by other artificial •:: means gives a resulting unstable : •iSoap unless treated. Of course, a •?high content of free fatty acids is a ?:sure test that the tallow is neither !?•resh nor clean, but of inferior !•i:quality. To-day, however, the supply •i!!'!•(•f a soap chip base from a reputable !:•:•::firm can give little rise to anxiety, •!ias a stable product of constant '!?quality grading is readily available. }.!•'! .: (b) If the "cleaning up" process ?.before saponification has been under- i•:•'J:aken, subsequent bleaching in the ,:. !i?i:.:boiling pan will be unnecessary. ??Bleaching in the boiler is convenient ii. land is common practice, although ii'.'the resulting soap stock after storage •i'•:.frequently proves unstable, so that !i:irancidity develops and no perfume :' •compound can, possibly cover the :il bad odour, even if used in great ii: quant ities. 'Another processing fault is fre- quently to be found in the drying, as '•'unless the soap is cut into very thin TOILET SOAP MANUFACTURE chips and adequate ventilation is employed throughout the lowering of the temperature change until cold, the soap stock again proves unstable. If the soap chips are "sacked" while still warm (and this can occur during heavy production days in the factory) heat develops once more in the centre of the sack and the chips may discolour or even char, and again odour value is greatly influenced. I would, how- ever, reiterate that a reputable firm takes all due precautions to guard against these possible deterior- ation problems. (c) Additives to soap stock likely to cause instability are both numer- ous and varied. Take the range of "fillers," for example, perfumery compounds, and unsuitable super- farting agents, etc. In fact, any addition, even if considered harmless, should not be made until a very- thorough test has been carried out. Fillers such as titanium and zinc oxides, etc., serving the dual purpose of both filler and whitening media, are widely used in the very cheap range of toilet soaps and are better omitted. If they are used, however, they should be incorporated by suspension in a. 10 per cent solution of either Tylose or Cellofas to produce a paste, which is added to the chips before working them in the mixing machine. Tylose or Cellofas addi- tions can also be made with the object of improving the malleability of soap chips, the use of 2 per cent of a 10 per cent solution protecting against brittleness and improving the plasticity and transparency of 229

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS the chips, to give ease in plodding and facilitate stamping-out-of the final soap tablet. The presence of any excess, how- ever slight, of alkali in the base, often causes perfumery difficulties, as alkalis saponify any esters used in the perfume compound. In the higher priced range of toilet. soaps, the use of cinnamic acid is a most satisfactory addition, for this acid acts as a neutraliser, antioxidant and fixative. To enumerate the various possibili- ties of deterioration caused by the use of perfume compounds is beyond the scope of this paper, as among the aromatic constituents used one can have both positive and negative catalysts present, aromatic alcohols and the esters thereof, certain ketonic bodies such as musk ketone then synthetics as, for example, ber/zaldehyde and in the formula- tion of a soap perfume the reactions of all ingredients must .be very carefully considered before use, with price considerations put entirely at one side until a satisfactory com- pound has been obtained. Then a cost adjustment may be made and by careful substitution of analogous replacement materials the desired cost price may be approached. I would once again emphasise, how- ever, that it is not always economical to employ cheaper products. Metallic contamination is the final cause of deterioration and, in particu- lar, contamination caused by copper base dies that are in poor condition either through neglect or wear and tear. All machines should be regu- 230 larly maintained and any signs of plate stripping be returned for replating, as only in this way can a perfect product be assured. The superfarting of toilet sokps is a well-known practice to-day,: whether milled or cold-processed soaps are being considered, and many combinations are possible. Lanolin, of course, was once the most favoured superfatting agent, but owing to" odour difficultie, s it has been replaced by various other ingredients. Prob-:!! ably one of the best is the use of emulsion compound of Polyethylene' ::!:i Glycol 1500, 'Mineral Oil (in traces), Wool Wax Alcohols, Oleyl .:: and Cetyl Alcohol. An even more:?• modern method is the use of phonated Cetyl/Oleyl Alcohols impart a remarkable smoothness t6 the soap base. ß COLORATION _AND DI The final subject in this br[• collection of notes must be : coloration of soaps, a matter:i great importance, as even the slighi I est discoloration in a white soap mar the product. Pastel shades popular and can suitably cover an, mild discolorations due to either soap base or the perfumery corn pound. It is the latter, when doubtful nature, that causes deterioration of a soap, as:ifil ß "faults" only develop upon agei• and are most unsightly either throUg spotting or just partial solid aromatic body should ever}:ii I• employed unless the whole of•:i i• crystalline derivatives have ei• been dissolved along with the no•