Liniments drying

Liniments Liniments are external preparations of a consistency thicker than water, but thinner than ointments, usually applied to the skin with a gentle rubbing of the hands. Liniments are among the oldest of dosage forms, along with related forms, such as plasters and ointments. The term came to its present use about 1600. Drying liniments are preparations which dry when smeared on the skin, forming a medicated film removable by water. 

Cajeput oil has been used in expectorant formulations and antiseptic and pain-relieving liniments, mouthwashes, shampoos, body washes, deodorants, acne products, barrier creams, lip balms, sunscreens, toothpastes, insect repellents, veterinary products, and others.The oil has been used in dentistry for relieving discomfort due to dry sockets also used as a fragrance component in soaps, detergents, creams, lotions, and perfumes, with maximum use level of 0.4% in the last category. 

Place approximately 5 ml of camphor liniment in a dried and weighed 120-ml Erlenmeyer flask and weigh accurately. Connect the flask with a U-shaped drying tube, place the flask and tube in an air-oven, maintained at 110°, and pass a steady stream of carbon dioxide through the U-tube into the flask for two hours. The orifice of the gas delivery tube should be about 15 mm above the surface of the liniment. Remove the flask, blow out the remaining carbon dioxide with dry air, cool the flask in a desiccator and weigh. The loss in weight is not less than 19 per cent and not more than 21 per cent of the camphor liniment taken for the assay. 

Add 7 ml of 10 per cent sodium hydroxide solution to 25 ml of liniment in a separator and extract twice with portions of light petroleum. Wash the light petroleum layers with water and add the washings to the main aqueous solution. Acidify with dilute sulphuric acid and extract the fatty acids with light petroleum, evaporate, add 5 ml of acetone, again evaporate, dry the residue at 80° for two hours, and weigh. 

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