BY DR. LAUDER BRUNTON. 557 



water-bath. The residue is boiled with absolute alcohol, and 

 the solution is concentrated to a small volume. On adding an 

 excess of ether to the alcohol, a precipitate occurs which con- 

 sists of the soda salts of the bile acids, and which, if set aside 

 for some time, often crystallizes. 



This precipitate may be obtained by decanting from it the 

 supernatant mixture of alcohol and ether. It is soluble in 

 water ; a few drops of the aqueous solution may be evaporated 

 to dryness in a porcelain capsule and then subjected to Petten- 

 kofer's test. This consists in adding a few drops of pure sul- 

 phuric acid, and then a trace of solution of cane sugar to it, 

 and heating very gently. After some time, an exceedingly 

 beautiful purple-violet coloration is developed. 



Bile acids may be detected in the urine without previous 

 separation by employing Strasbourg's method (see 140), but 

 Hoppe-Seyler's method just described is much more reliable. 



205. Detection of Blood in Urine. Urine which con-/^, 

 tains blood, on being allowed to stand, usually furnishes a de- , 

 posit in which characteristic blood corpuscles may be discovered n , ' 

 without difficulty. 



On examining such urine by means of the spectroscope, there 

 is usually no difficulty in observing the spectrum of hsemoglo- 

 bin or of hrematin. 



Urine which contains haemoglobin furnishes, when boiled, a 

 precipitate of albumin and haematin. 1 



1 Although it lins been considered adivisable to devote some space to 

 the mode of detecting a few of the more important abnormal constituents 

 of urine, it would be beyond the object of this book to give a complete 

 account of the properties of, and mode of separating, all the substances 

 which occur in urine in a state of disease. Any additional information 

 on these subjects is to be found in the very valuable " Handbuch der 

 physiologisch- imd pathologisch-Chemirchen Analyse" of Professor 

 Hoppe-Seyler, to which reference has been already made. 



