COMPOUND ANLVIAL SUBSTANCES. 97 



of zinc will be obtained by evaporation. The extractive matter 

 and hffimaphoein will be left as a residue. 



If neither bilin, biliverdin, nor the acids of the bile are pre- 

 sent, the investigation may be much simplified. The soda may 

 be separated from the alcoholic solution as a sulphate ; we may 

 evaporate, separate the fatty acids by means of water, boil the 

 residue with carbonate of zinc, and filter the solution. By this 

 means we can separate the lactic acid. The urea may be se- 

 parated from the alcohol-extract by oxalic acid, of which any 

 excess may be removed by digestion with carbonate of lead. 



We may be easily convinced of the presence of the alcohol- 

 extract by observing the precipitates which are thrown down 

 by the addition of infusion of galls and a solution of iodine. 



The bases, which were present in the alcoholic solution in 

 combination with acids, are now combined with sulphuric acid. 

 Tliej usually are soda and potash. 



7. The residue of (6), which was not taken up by absolute 

 alcohol, must now be treated with alcohol of -883, which will 

 take up sugar of milk, diabetic sugar, spirit-extract (which is 

 usually of a brown colour in consequence of the presence of 

 hsemaphsein,) chloride of sodium, phosphates, and probably lac- 

 tates. If the quantity of sugar (of either of the above kinds) 

 is not very minute, a portion of it will usually crystallize either 

 on the cooling of the spirituous solution or by spontaneous 

 evaporation. The presence of the sugar may, however, be easily 

 recognized by the sweet taste of the spii'ituous solution after 

 evaporation. If the solution be evaporated to the consistence 

 of an extract, and then treated with cold alcohol of -850, the 

 greater part of the sugar will remain undissolved, while most of 

 the extractive matter will be taken up. The presence of the 

 extractive matter may be determined partly by the brown colour 

 of the spirituous solution, and more decidedly by the precipi- 

 tates which are caused by the addition of bichloride of mercury, 

 acetate of copper, and tannin. The spirit-extract usually evolves 

 during evaporation a peculiar odour, somewhat resembling that 

 of toasted bread. On evaporating a portion of the spirituous 

 solution to dryness, and incinerating the residue, the ash will 

 be found to consist of chloride of sodium, phosphates, and (if 

 any lactates are present) carbonates of potash and soda. These 

 may be separated in the ordinary manner. 



7 



