Soaps titre

An alcoholic soap solution (white Marseilles soap in about 60% alcohol, see Water, Vol. I) is prepared of such concentration that 1 c.c. corresponds with 0-0005 gram of CaO. The titre is controlled by means of barium chloride solution containing 0-436 gram of crystallised barium chloride per litre 40 c.c. of this solution should require 8 c.c. of the soap solution to form a persistent froth after agitation. 

In the first method, 100 ml of water is placed in a 200 ml stoppered flask. 1 ml of standard Wanklyn s soap solution is added at a time until a lather is obtained on shaking which persists for one minute. If the titre on 100 ml of water is T ml, since 1.0 ml of standard soap solution = 1.0 g CaCO. ... 

The titre of a soap or a fat is the temperature at which its fatty acid solidifies. As a rule the melting points are not clearly defined because the fatty acids are mixtures. A few examples of titres are given below (°C) ... 

The soaps with low titre are more soluble in water at low temperatures.. nimal fibres are usually scoured at temperatures not in excess of 60°C, and therefore a low-titre soap is preferred. Olive-oil soap is the most suitable, but also the most expensive, so that soaps made from coconut or cotton-seed oils are often used. Cellulo c fibres, on the other hand, can be scoured at the boil, and the lack of solubility of a high-titre soap does not matter. A high-titre product such as tallow soap is used, this being a more effective detergent. 

After boiling, the goods are washed with water, and then treated with a dilute solution of hydrochloric acid (1 -5 to 2 per cent). This liberates the fatty acids from the lime soaps and pectic acid from the pectates, with the formation of calcium chloride. The goods are then rinsed to remove the calcium chloride and returned to the kier where they are boiled again with sodium carbonate and rosin or a high-titre soap. The free fatty and pectic acids are now converted into their soluble sodium salts which can be washed away with water. 

Titre of mixed fatty acids contained in the soap 30°C (86°F) maximum... 

Prom the data obtained by estimating the titre, iodine number, and saponification equivalent of the mixed fatty and rosin acids, and the rosin content, a fairly good idea of the constitution of the soap may be deduced. 

If the titre of soaps containing carbolic acid or mineral oil is required the carbolic acid and mineral oil must be removed the former can be removed by heating the soap at 100° to 105° and the latter by extracting the soap with ether. 

---