Neutral soap

Metal soaps are composed of a metal and acid portion suppHed as solutions in solvent or oil. The general formula for a metal soap is (RCOO). In the case of neutral soaps, x equals the valence of the metal M. Acid soaps contain free acid (positive acid number) whereas neutral (normal) soaps contain no free acid (zero acid number) that is, the ratio of acid equivalents to metal equivalents is greater than one in the acid soap and equal to one in the neutral soap. Basic soap is characterized by a higher metal-to-acid equivalent ratio than the normal metal soap. Particular properties are obtained by adjusting the basicity. 

Oxalate Acid Number. A metal soap solution is treated with a measured excess of organic acid. Potassium oxalate solution is added to precipitate the metal and the total sample is back-titrated with alkaU to determine its acidity. Acidity is expressed ia acid number units, equivalent to mg KOH per g. A neutral soap gives a 2ero acid number, an acidic soap solution a positive acid number, and a basic soap solution a negative acid number. 

Neutral soaps Neutral spints Neutramyan [1404-08-6] Neutrase Neutnno... 

Addition of alkali suppresses the hydrolysis, and when sufficient alkali has been added for complete suppression of hydrolysis, the adsorbed layer consists of neutral soap. This is probably the state of affairs at the maxima of surface tension in Fig. 32. More alkali is required to reach the maximum with the stronger solutions, because more alkali is needed to suppress hydrolysis completely. The maximum surface tensions in Fig. 32 are probably very near to the surface tension of solutions of neutral soap only of the concentration indicated on each curve. The subsequent slow fall of tension, as more alkali is added, is probably due to a salting out of the soap by the alkali, an increase in escaping tendency caused by the presence of comparatively large amounts of another solute. It would be interesting to find whether addition of neutral salt, in addition to the small amount of alkali needed to reach the maximum, produces a fall in tension similar in amount to that given by additional alkali. 

So-called neutral soap solutions are more complex systems than at first appears, and the fairly small amounts of hydrolysis in the interior of the solution are very much magnified by the great difference in adsorbability between a neutral soap and an acid soap, or free fatty acid. A close approximation to the true surface tension-concentration curve of neutral soap can probably be obtained by plotting the maxima of tension shown in Fig. 32 against the concentration on each curve. It does not seem possible as yet to plot the true surface tension-concentration curve for acid soap, as the concentration of acid soap, and even the ratio of acid to soap molecules in any compound which may be formed in the interior, is unknown. 

The composition of the soap solution used has a great influence on the stability and properties of the films. For good results very highly purified oleic acid must be used and the best results cannot apparently be obtained without the use of a trace of ammonia or an amine. Excess of alkali is said to be fatal this points to the hydrolytic equilibrium between acid and neutral soap being of great importance. A 5 per cent, solution of ammonium oleate in 50 per cent, glycerine makes a good solution for ordinary work details of this may be found in Lawrence s Soap Films. Perrin, however, used a 2 per cent, solution of ordinary soap ... 

A typical Mazzoni fatty acid neutralization soap plant is illustrated in Fig. 36.5.6 The operation of this plant involves the pumping of the reactants through preheaters to a turbodisperser, or high-shear mixer, where the contact of the reactants with each other initiates the formation of neat soap. The soap mass, which is partially reacted at this stage, then proceeds to the mixer where it is recirculated until the neutralization is complete. The completion of the neutralization reaction is monitored continuously by an electric potential (millivolt, mV) measurement for alkalinity. The neat soap is then dried by vacuum spray-dryers, as described earlier, to produce soap pellets ready for finishing into soap bars. 

The patient then applies the rest of the post-peel cream to the face, after washing with neutral soap or cleansing lotion. 

A-M is the neutral salt of an acidic detergent substrate and may also be referred to as the soap or surfactant. The normally neutral soap can also be slightly acidic... 

When soap is produced from most triglyceride saponification or fatty acid neutralization soap-... 

Kottula s Soaps.—K. departure from the ordinary system of Boap-raaking was introduced by Dr. Hottnla about twenty five years ago, and at the time attracted much attention. In conducting his process, Kottula adds to ordinary curd, mottled, yellow, or other soaps, made in the ordinary way, fatty matters, lime liquor, concentrated soda leys and alum, with the object of producing a cheaper neutral soap than he believes was hitherto produced. The fatty matters he employs are such as are commonly used by soap-makers. He first boils soda leys until they have acquired the strength of about 30 B., and then adds to them alum, in the proportion of about lbs. to each owt. of ley. He then prepares a lime liquor by adding to any requisite quantity of water as much lime as it will absorb or take up, and to this lime solution he adds sal ammoniac in the proportion of about half a pound to each owt. of the solution. Sometimes he omits the sal ammoniac. 

The lime liquor is prepared as before, with the addition of to lb. of sal ammoniac, the whole being boiled for half an hour. After resting until quite clear, ten tons of fatty matter, with or without resin, and nine tons of the leys as above prepared (or smaller quantities in the same proportions), are said to produce a superior compact neutral soap, which may he coloured, mottled, or perfumed in the ordinary manner. The rationale of this Tocess is not apparent. If sal ammoniac is boiled with ime-water, it is quickly decomposed. The addition of alum to soda leys effects merely the formation of sulphate of soda and of alnminate of soda, which, if needed, can l>e procured more cheaply (see page 229). 

The proportwne employed by the inventors are thus given carbonate of soda (English) at 48° water, 100 lbs. lard, tallow, or oil, 100 lbs. ] 27 lbs. of carbonate of soda will, it is said, make a neutral soap for soft water. The product obtained by the above... 

In the new reactions of which we speak it will be understood that water, at a temperature of from 311° and 329° F., decomposes a neutral soap into on acid soap and very basic soap, and that the latter acts in a secondary manner on a fresh quantity of fatty matter in the same manner that a free alkali would do. The observations of. Chevreul, relative to the action of water on soaps, accord with this explanation. 

It must be admitted that the saponification of suet by means of 4 per cent, of its weight of lime presents several distinct phases in which a basic or neutral soap is formed at first and is then ohang ed into a relatively acid soap. 

Blake and BCaxwell s Process.— By this process a soap is produced by combining soap in the state called " sort curd, with a hydrated soap, or neutral soap not deprived of its water. The curd soap may he prepared as usual, but the patentees prefer that it should be made with soda leys of the strength and in the proportions given below, whereby a soft curd is obtained which is better adapted for combining with neutral soap. The soap thus formed may be separated from the water, or excess of ley, by cutting the pan in the usual way either by means of salt or strong leys. The resin soap is prepared as follows - -A.bout one-third of the resin to be used is mixed with a... 

Although it is possible, with care, to produce neutral soaps of good appearance and firm touch by this method, cold-process soaps are very liable to contain both free alkali and unsaponified fat, and have now fallen considerably into disrepute. 

Depending on the metal atom valence and on the synthesis process, various types of soap molecules can be obtained. In the case of stoichiometric additives, also called neutral soap, soap molecules syntheses will correspond to the following reactions [17, 18] ... 

Kralchevsky, P. A., Danov, K. D., Pishmanova, C. I. et al. (2007) Effect of the precipitation of neutral-soap, acid-soap, and alkanoic acid crystallites on the bulk pH and surface tension of soap solutions source. Langmuir, 23, 3538—3553. 

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