Stearic acid and sodium stearate

A method is described in Method 54 for the determination of stearic acid and sodiiun stearate in styrene butadiene. 

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An analytical solution for molecules with alkaline functionality is acid/base titration. In this technique, the polymer is dissolved, but not precipitated prior to analysis. In this way, the additive, even if polymer-bound, is still in solution and titratable. This principle has also been applied for the determination of 0.01 % stearic acid and sodium stearate in SBR solutions. The polymer was diluted with toluene/absolute ethanol mixed solvent and stearic acid was determined by titration with 0.1 M ethanolic NaOH solution to the m-cresol purple endpoint similarly, sodium stearate was titrated with 0.05 M ethanolic HC1 solution [83]. Also long-chain acid lubricants (e.g. stearic acid) in acrylic polyesters were quantitatively determined by titration of the extract. 

METHOD 54 - DETERMINATION OF STEARIC ACID AND SODIUM STEARATE IN STYRENE-BUTADIENE RUBBER SOLUTIONS. TITRIMETRIC PROCEDURE. 

This titrimetric procedure is capable of determining down to 0.01% of stearic acid and sodium stearate in styrene-butadiene rubber solutions. 

A typical salt is sodium stearate. This is the salt of stearic acid and sodium hydroxide. The formula of stearic acid is CjjHjjCOOH and the formula of sodium stearate is Na+Cj HjjCOO". 

Fatty-acids, salts and esters Aluminum monostearate, calcium stearate, ethyl oleate, isopropyl myristate, isopropyl palmitate, magnesium stearate, oleic acid, polyoxyl 40 stearate, proprionic acid, sodium stearate, stearic acid, purified stearic acid, and zinc stearate... 

The plasticizing effects of a larger number of metal stearates on the zinc sulfonate ionomer were examined, and the results are given in Table III in terms of flow and mechanical properties. Lead stearate, zinc stearate, and ammonium stearate significantly improved melt flow along with the stearic acid control. The barium, magnesium, sodium, lithium, and calcium stearates showed little, if any, improvement in melt flow. Of the four melt flow improvers, both stearic acid and ammonium stearate exerted deleterious effects on tensile properties. Only the zinc and lead stearates substantially improved tensile properties. Thus, while zinc stearate is not unique, the number of fatty acid derivatives that improve both melt flow and mechanical properties is limited. 

More examples can be foimd in references. In two traditional sodium aspirin tablet formulations, stearic acid and magnesium stearate are used as lubricant in the concentration of 1.5% and 0.3%, respectively [12]. 

As seen from Table 5.3, the products modified by tita-nate NDZ-101, sodium stearate, stearic acid, and Zinc stearate acid zinc exert the highest activation index nevertheless, the modification effects of other modifiers are relatively poor. The results of contact angle also support this point. Among these four modifiers, sodium stearate modified products hold the maximum contact angle and have lower costs. ... 

Natural soaps are the sodium and potassium salts of fatty acids. They are produced as a result of the interaction of a caustic alkali and a fat. A typical animal or vegetable fatty acid molecule consists of a long hydrocarbon chain with a terminal carboxyl group. For example in the case of sodium stearate, which was introduced as an example in section 1.6, the fatty acid is stearic acid and it has the chemical formula CH3(CH2)i6COOH. The chemical reaction of stearic acid and sodium hydroxide results in the soap sodium stearate, Ci7H35COO Na+. The commonly occurring fats are lauric, myristic, palmitic, stearic, oleic, etc. Common bars of washing soap will consist of a number of pure soaps. 

Soaps Substances formed by saponification. In this reaction, the oil or fat (glyceryl ester) is hydrolysed by aqueous sodium hydroxide to produce the sodium salt of the fatty acid, particularly sodium stearate (from stearic acid). Soap will dissolve grease because of the dual nature of the soap molecule. It has a hydrophobic part (the hydrocarbon chain) and a hydrophilic part (the ionic head) and so will involve itself with both grease and water molecules. However, it forms a scum with hard water by reacting with the Ca2+ (or Mg2+) present. 

Stearic acid is insoluble in water, and sodium stearate (a soap) is soluble. What causes the difference in solubility Explain. 

Sodium stearyl fumarate is supplied in a pure form and is often of value when the less pure stearate-type lubricants are unsuitable owing to chemical incompatibility. Sodium stearyl fumarate is less hydrophobic than magnesium stearate or stearic acid and has a less retardant effect on tablet dissolution than magnesium stearate. A specification for sodium stearyl fumarate is contained in the Food Ghemicals Godex (FGC). 

An aqueous solution of zinc sulfate is added to sodium stearate solution to precipitate zinc stearate. The zinc stearate is then washed with water and dried. Zinc stearate may also be prepared from stearic acid and zinc chloride. 

The topical lotion contains clindamycin phosphate USP at a concentration equivalent to 10 mg clindamycin per milliliter. The lotion contains cetostearyl alcohol (2.5%), glycerin, glyceryl stearate SE (with potassium monostearate), isostearyl alcohol (2.5%), methylparaben (0.3%), sodium lauroyl sarcosinate, stearic acid, and purified... 

Organic acids containing long carbon chains are known as fatty acids . The neutralization of fatty acids by alkalis produces salts which are soapy to the feel. Fatty acids are present on our skin, and this explains why alkalis feel soapy. Sodium stearate (common soap) is produced by neutralising stearic acid with sodium hydroxide. (For more about soap, see page 175.)... 

Zinc stearate was synthetized [64] by precipitation method through steps neutralization of stearic acid by sodium hydroxide then double decomposition using zinc sulfate to precipitate zinc stearate. It was concluded that zinc stearate can be used as activator for sulfur vulcanization process instead of ZnO and stearic acid in absence and presence of fillers. 

Stearic acid and its derivatives such as magnesium stearate and sodium stearyl fumarate are used as the lubricants of choice for the production of solid dosage forms. They improve density, stickiness, and flow to powdered excipient-drug mixtures. Further, they are used as a binder that helps tablets hold together and break apart properly. In this chapter, the effect of stearic acid, magnesium stearate and sodium stearyl fumarate on the particle and tableting properties of model excipients such... 

Figure 1. Chemical structure of stearic acid and derivatives (A) Stearic acid, (B) magnesium stearate and (C) sodium stearyl fumarate.

The pre-treatment of a filler surface changes fhe interface, and thus it is expected to affect the properties of adjacent phases extending some way into the bulk. There are examples of using the various surface modifiers such are acids and acid precursors, alkoxysilanes, organofitanates and related compounds, stearic acid and others." How the surface pre-treatment of CaCOs filler by sodium stearate changed fhe adhesion parameters in the PVAc composite is illustrated in Table 1 The adhesion parameters could be used to relate the interactions at the interface to the mechanical properties of the composite. For example, the small absolute decreases in the work of adhesion after the pre-treatment can lead to the proportionate large absolute decreases in fracture energy. 

Metallic stearates, or soaps, are metal salts of organic acids like stearic acid. Calcium and zinc stearates are commonly used, although aluminum, iron, lead, lithium, magnesium, sodium, nickel, and potassium stearates are sometimes found in plastics. Stearates are most commonly used in thermoset polyester molding compounds, but calcium stearate has been used as a lubricant and release agent in polypropylene and ABS. Zinc and sodium stearates are used in polystyrene, SAN, and nylon. Stearates are not recommended for polycarbonate because of discoloration. Recommended loadings are usually 1 percent or less, but up to 5 percent has been used at times. 

Uncoated tablet materials, lactose, liquid glucose, mannitol, stearic acid, starch, calcium stearate, talc and sucrose could be tolerated in the precipitation solution without interference. As gelatin and polyvinylpyrrolidone precipitate with sodium tetraphenylboron it is not possible to apply the method to tablets containing these materials. 

Soaps are made by heating sodium hydroxide with a fat such as coconut oil, olive oil, or beef fat, which contain esters formed between glycerol and fatty acids (see Section 19.7). The sodium hydroxide attacks the esters and forms the soluble soap. In the case of beef fat, stearic acid forms the soap sodium stearate, seen in (3). Soaps, however, form a scum in hard water. The scum is an impure precipitate of calcium stearate. 

The most effective lubricants are the hydrophobic stearates, such as magnesium stearate, calcium stearate, and stearic acid. Magnesium stearate is the most widely used lubricant [117,118]. Lubricants proposed as being less hydrophobic such as hydrogenated vegetable oils, polyethylene glycols, and sodium stearyl fumarate are less effective in this application [118]. 

Sodium, potassium, and calcium salts of ascorbic acids are called ascorbates and are used as food preservatives. These salts are also used as vitamin supplements. Ascorbic acid is water-soluble and sensitive to light, heat, and air. It passes out of the body readily. To make ascorbic acid fat-soluble, it can be esterified. Esters of ascorbic acid and acids, such as palmitic acid to form ascorbyl palmitate and stearic acid to form ascorbic stearate, are used as antioxidants in food, pharmaceuticals, and cosmetics. 

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