BITTER PRINCIPLE 



351 



magnesia, in the diarrliooa accompanying phthisis, and ho thinks that both in efficacy 

 and safety, it surpasses our most approved remedies for that complaint. I have used 

 it with advantage, in the form of ointment, applied to the septum nasi, in ulcoratiou 

 of this part, and as a local remedy in chronic skin diseases.' 



Much of the sub-nitrate of bismuth of tho shops has been found to contain nitrate 

 of silver. 



BISTRE. (Bistre, Fr. ; Sister, Ger.) A brown colour which is \iscd in water- 

 colours, in tho same way as China ink. It is prepared from wood-soot, that of beech 

 being preferred. The most compact and best-burned parcels 'of soot are collected 

 from tho chimney, pulverised, and passed through a silk sieve. This powder is 

 infused in pure water, and stirred frequently with a glass rod, then allowed to settle, 

 and the water decanted. If the salts are not all washed away, the process may bo 

 repeated with warm water. Tho paste is now to be poured into a long narrow 

 vessel filled with water, stirred well, and left to settle for a few minutes, in order to 

 let the grosser parts subside. Tho supernatant part is then to' bo poured off into a 

 similar vessel. This process may be repeated twice or thrico, to obtain a very good 

 bistre. At last tho settled deposit is sufficiently fine, and, when free from its super- 

 natant water, it is mixed with gum-water, moulded into proper cakes and dried. It 

 is not used in oil-painting, but has the same effect in water-colours as brown pink has 

 in oil. 



Dr. MacCulloch objects to soot as a source of bistre, both from tho carelessness 

 used in collecting it, and the uncertainty of tone and colour. If the liquids resem- 

 bling tar, obtained from the distillation of wood, be again carefully distilled, water, 

 acetic acid, and hydrocarbonaceous substances, as naphtha, pass over, and leave a resi- 

 duum brown or black, pitch-like, or brittle according to the time and temperature 

 employed ; by prolonging the heat with care, the brittle substance becomes a powder. 

 Dr. MacCulloch states that, by care, bistre from wood-tar may be obtained, having tho 

 fine properties of sepia with great depth of colour. 



The remarkable bronze-like varnish, with almost a metallic lustre, seen upon tho 

 interior of Highland cottages, arc bistre-deposits from the smoke of peat. 



BITTER-ALMOND Oil.. See ALMOND OlL. 



BITTER-ALMOND WATER. Water containing the oil of bitter almonds in 

 solution. It should be prepared by distillation from the bitter almonds. It is how- 

 ever frequently made by first rubbing the essential oil of bitter almonds with mag- 

 nesia and mixing this with water; or a solution of the oil in spirits of wine is simply 

 added to tho water and they are shaken together. 



BITTER CUPS. Wooden cups in which water or other liquid is allowed to 

 stand until it acquires a bitter taste, and thus serves medicinally as a tonic. These 

 cups are turned in 'bitter wood,' or wood from a West Indian tree tho Picrcena 

 excclsa, Ldl., and from other plants belonging to the quassia order. 



BITTERN. The mother-liquor of sea-water left after the crystallisation of tho 

 less soluble salts. The bittern is used as a source of bromine. 



BITTER PRINCIPLE. (Amer, Fr. ; Bitterstoff, Ger.) The ' bitter principles ' 

 consist of bodies which may be extracted from vegetable productions by tho agency 

 of water, alcohol, or ether. These are not of much importance in the arts, with a few 

 exceptions. Lupulin, the bitter principle of the hop, for example, is used for pre- 

 serving beer. 



Quassin is the bitter principle of quassia ; Absinthin, that of wormwood ; and 

 Gentianin, that of Gentian. These are sometimes substituted for tho hop. 



For particulars of these, and numerous other bitter principles, see ' Watts's Dic- 

 tionary of Chemistry.' 



The following list gives the more important of the bitter substances which have 

 been used in the arts and in medicine. (See the articles respectively) 



