BY DR. LAUDEll BRUNTON. 455 



Put liquor sodre in a watch-glass with a little chloride of 

 lime ; stir it, and introduce a portion of xanthine. A ring will 

 form round it, at first dark green, but soon becoming brown, 

 find then disappearing. 



67. Uric Acid. Suspend the lead precipitate (a) in water ; 

 decompose it completely b}' hydrogen-sulphide; filter; concen- 

 trate the filtrate in a water-bath. Uric acid will separate gradu- 

 ally. 



Filter, and set the filtrate aside (d). Wash the crystals on 

 the filter with a little water and then with alcohol. If desired, 

 they may be further purified by dissolving them in a little 

 liquor sodae, precipitating by ammonium cliloridc ; filtering and 

 decomposing by dilute hydrochloric acid. 



Murexide Test. Put a small portion of uric acid on a watch- 

 glass, with one or two drops of nitric acid, and evaporate to 

 dryness at a moderate temperature. A yellow residue will re- 

 main, which becomes red when quite dry. Put a drop of am- 

 monia on the side of the glass, and let it run gently down to 

 the uric acid, which will then become of a beautiful purple. If 

 a drop of liquor potassrc or liquor sodoe is used instead of am- 

 monia, a bluish-violet color will be produced. 



Inosite. Evaporate the filtrate (d) till a permanent tur- 

 bidity is produced by the addition of alcohol. Then add its 

 own volume of alcohol to it and warm it, when the turbidity 

 will disappear. Set it aside for several days. Inosite may 

 then crystallize out. If it does not, add ether ; and if still no 

 crystals form, evaporate almost to dryness ; add a little nitric 

 acid, evaporate to dryness ; moisten it with calcium chloride, 

 and evaporate to dryness again. If inosite is present, a rosy 

 red spot will remain. 



If crystals have been formed, dissolve some in water, in which 

 the}- are easily soluble, and apply the same test. 



68. Brain. The brain contains cholesterin, lecithin, and 

 cerebrin, besides albuminous substances, which chiefly form the 

 axis cylinders, and are insoluble in water. Cerebrin probably 

 belongs to the white substance of nerves. 



The specific gravity of the brain may be ascertained in the 

 manner directed in App. 216, and the amount of water it 

 contains by weighing it, drying it in a hot chamber, or over 

 sulphuric acid, and estimating the loss. To separate the sub- 

 stances contained in the brain, remove the membranes and ves- 

 sels as much as possible from it, wash its surface with water, 

 and rub it to a paste in a mortar. Mix it with great excess of 

 alcohol, and let it stand for several days, stirring it frequently. 

 Separate the alcohol by filtration, and set it aside for the pre- 

 paration of lecithin (a) 



Rub up the brain again, and extract it with large quantities 

 of ether, as long as the}' take up much lecithin or cholesterin. 



