HARD PETKOLATUM 349 



marsh-gas series, obtained by distilling off the lighter and 

 more volatile portions from petroleum, and purifying the 

 residue when it has reached the desired melting point. 



Properties. — A fat-like mass of about the consistence of 

 an ointment, varying in color from yellowish to light amber, 

 having not more than a slight fluorescence, even after being 

 melted; transparent in thin layers, completely amorphous, 

 and without odor or taste ; or giving off, when heated, a faint 

 odor of petroleum. 



The melting point of petrolatum ranges between 45° 

 and 48° 0. (113° and 118.4° F.). In other respects soft 

 petrolatum has the solubility of liquid petrolatum. 



Peteolatum Album. White Petrolatum. 



A colorless mixture of hydrocarbons, chiefly of 'the 

 methane series, obtained by distilling off the lighter and more 

 volatile portions from petroleum, and purifying the residue. 

 A white, unctuous mass, of about the consistency of an oint- 

 ment, transparent in thin layers, completely amorphous; 

 without odor or taste. Otherwise it resembles, in solubility, 

 petrolatum. 



Action and Uses. — Petrolatum is a valuable emollient. 

 It soothes, protects and softens parts to which it is applied, 

 and is superior to animal and vegetable fats and oils in not 

 becoming rancid, and therefore irritant and malodorous. 

 Petrolatum may be used alone, or as an excipient in the 

 preparation of ointments, but does not aid the absorption of 

 drugs (as do alcohol, glycerin, chloroform, and animal oils 

 and fats), for it is not itself absorbed even when adminis- 

 tered internally. Petrolatum exerts a demulcent action 

 upon the mucous membrane of the alimentary tract, and 

 may be prescribed in electuary or capsule in inflamma- 

 tion thereof. Petrolatum is sold universally under the pro- 

 prietary names of vaseline and cosmoline, and is often com- 

 bined with antiseptics for medicinal and surgical purposes 

 ^n skin diseases and upon inflamed mucous membranes, 

 blistered and abraded surfaces and sores. It is one of the 

 most useful agents in lubricating instruments, protecting 



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