726 OINTMETSTTS OLEATES 



brittle. They are mostly colourless, but have a powerful 

 odour, and distinctive often aromatic taste. They are 

 insoluble, or only slightly soluble, in water, but are readily 

 soluble in alcohol, ether, fatty and mineral oils. They are 

 mostly lighter than water. Most boil between 302-382 

 Fahr., but the boiling point of camphors is about 372 Fahr. 

 All are acted upon by oxygen, and distil unchanged. They 

 are obtained by distillation, or by extraction. The volatile 

 oils are antiseptic and stimulant, and are used as carmina- 

 tives, antispasmodics, and parasiticides, and for flavouring. 



The Camphors, thymol, menthol, and common camphor 

 are oxygen derivatives of volatile hydrocarbons. In 

 physiological action they are allied to the volatile oils. 



Oleo-resins, such as crude turpentine, Canada balsam, and 

 Frankincense, are natural mixtures of volatile oil and resin. 



Balsams are vegetable exudations consisting of resins 

 with benzoic or cinnamic acid, dissolved in volatile oils. 



Mineral, paraffin, or petroleum oils are a series of paraffin 

 hydrocarbons, obtained from the distillation of shale, coal, 

 and other geological deposits, and having the formula 

 C u H 2n+2 . (See Petroleums.) The several members differ 

 in their boiling point, and are separable by distillation. 

 Methane, or marsh gas (CH 4 ), and several of the simpler 

 members are gaseous, and used for heating and illumination. 

 Others, such as pentane (C 5 H 12 ), and hexane (C 6 H 14 ), are 

 known as petroleum spirit, are solvents for fats, resins, and 

 indiarubber, and are used for making varnishes. Heptane 

 (C 7 H 16 ), known as benzoline, paraffin oil, or mineral sperm 

 oil, is used for burning. Nonane and dodecane are em- 

 ployed as lubricants. Hexdecane (C 16 H 34 ) is the chief 

 constituent of vaseline and other soft paraffins. It is used 

 as a bland protective, and for the making of ointments. 

 The solid, hard, or wax paraffins, melting at 110-145 Fahr., 

 are substituted for wax in the making of ointments. 



OINTMENTS-OLEATES-LINIMENTS-CERATES- 

 PASTBS 



Ointments or unguenta are semi-solid mixtures of drugs 

 with fatty matters, and are used externally. The excipients 



