ASTRINGENTS. 57 



The Mineral Acids. 



Usually classed among the tonics. 



Sulphuric Acid. — Employed only in medicine in a state of solu- 

 tion. Acts as a tonic, astringent, and refrigerant ; used in low forms 

 of fever, and to check excessive perspiration. The dilute acid of the 

 Phar. contains f3j of the concentrated acid, to fSxiij of water; dose, 

 10 to ':{0 drops, in a wineglass of water. The elixir vitriol^ or aro- 

 matic sulphuric acid, contains ginger and cinnamon ; it is much 

 used in the hectic fever of phthisis, and in convalescence from acute 

 disorders. Dose, the same. 



There is also an ointment. 



Nitric Acid is tonic and refrigerant ; never used in its pure state ; 

 two kinds kept in the shops, the nitric which is colourless, and the 

 nitrous., which is reddish. Used as a tonic in low forms of fever. 

 Dose 2 to 10 drops, according to its strength. A strong solution is 

 used externally to indolent ulcers. Hope's mixture consists of nitric 

 acid, laudanum, and camphor water ; — used in dysentery, &c. 



Muriatic Acid. — Colourless when pure ; used in a dilute form in 

 low forms of fever, especially in typhus fever. Dose, 5 to 20 drops, 

 in a wineglass of water. Used also as a gargle in scarlet lever. 



Nitro- Muriatic Acid. — Made by mixing one part of nitric with 

 two of muriatic acid ; mutual decomposition ensues, by which nitrous 

 acid fumes are given off, and chlorine remains dissolved in water. 

 It is thought to have an especial tendency to the liver, and is given 

 in hepatic diseases ; also in secondary syphilis. Used likewise as a 

 bath, or foot-bath, in these disorders. The solidion of chlorine some- 

 times used in bronchitis ; also the vapour of chlorine inhaled, but 

 apt to occasion irritation. 



CLASS IV. — ASTRINGENTS. 



Def. — " Medicines which produce contractility of the living tissues." 

 They occasion this effect whether taken internally, or locally applied. 

 They also gently, but permanently, stimulate the system, causing a 

 harder and fuller pulse, and at the same time producing a constringing 

 effect upon secreting or bleeding orifices. They may be conveniently 

 divided into the two classes of Vegetable and Mineral astringents. 

 The former depend for their astringency on a principle common to 

 all of them, named tannic acid ; the latter possesses no such com- 

 mon principle, but each one of them is peculiar in its effects upon 

 the system. 



Tannic Acid — Tannin. — Exists in the vegetable astringents in 

 combination with gallic acid. It is best obtained by the action of 

 commercial sulphuric ether on powdered galls, allowing it slowly to 

 percolate through them ; the water of the ether dissolves out the 

 tannic acid, which may be separated by evaporation. 



Pro'p. — A light porous substance, of a yellowish-white colour ; 



