320 MERCURY. 



and the deutoxide or peroxide, which is of a red colour, and con- 

 tains twice as much oxygen as the protoxide, consisting of 200 

 mercury-f-16 oxygen. Of these, the former is comparatively mild, 

 and appears to be the active ingredient in the pilulce liydrargyri, 

 or blue pill ; in the hydrargyrum cum creta, and in the unguentum 

 liydrargyri, or mercurial ointment. The latter, or red oxide of 

 mercury, is a virulent poison ; it is now, therefore, seldom, if ever, 

 administered internally. 



Black Oxide, or Protoxide of Mercury. — Hydrargyri 

 oxidum cinereum, Ph. L. — The London College directs this to 

 be prepared by boiling one ounce of chloride or sub-muriate of 

 mercury in a gallon of lime-water, stirring it constantly until the 

 oxide of mercury falls down. The precipitate must then be washed 

 with distilled water, and dried by a gentle heat. The black or 

 grey oxide of mercury was formerly called JEthiops per se, and 

 is designed to be used as a substitute for those preparations in which 

 the mercury is oxidated by trituration ; but it varies considerably 

 in chemical composition, and is scarcely ever prescribed. It is 

 given in the dose of from one to three grains twice a-day, usually 

 under the form of pill. The protoxide, as it exists in the Pilulce 

 hydrargyri or blue pill, is by farlhe best preparation for obtaining 

 the general action of the metal upon the system. Three grains of 

 the mass contains one grain of the mercury ; and the usual dose is 

 from six to ten grains twice a-day until the mouth be affected. In 

 larger doses it appears to increase the secretion of bile, and acts as 

 a cathartic ; hence it has been recommended as an occasional 

 purgative conjoined with extract of colocynth, rhubarb, or aloes, 

 where from the deficiency or morbid state of this secretion, the 

 alvine evacuations are clay-coloured or white, attended with gene- 

 ral languor, drowsiness, or general inactivity of the system. Two 

 or three grains of blue-pill, given at bed-time, is a favorite remedy 

 with some practitioners in dyspepsia, especially where the stools 

 are clay-coloured ; and it is beneficially employed to excite the 

 action of the absorbents in dropsies, conjoined with digitalis 

 or squill. By triturating mercury with chalk, it forms the 

 Hydrargyrus cum creta, a preparation which is frequently pre- 

 scribed as a mild alterative for children in tabes mesenterica, 



