306 URINE. [CH. XII. 



or genital organs it often forms a clot. In haematuria the 

 urine often has a characteristic smoky appearance, and it 

 is always associated with albuminuria. Haemoglobinuria 

 is a result of haemolysis. It therefore follows a variety 

 of infectious diseases, transfusion of blood, the absorption 

 of haemolytic substances, such as many aromatic com- 

 pounds, severe burns and scalds. Methaemoglobin is 

 nearly always present. 



The simplest method of detecting blood is by means 

 of the benzidine test, provided that the necessary reagents 

 are to hand. 



374. Heller's test. Boil 10 cc. of urine with a little 40 

 per cent, sodium hydroxide, and allow the tube to stand for a while. 

 A red deposit indicates the presence of blood-pigment in the urine. 

 Pour off the supernatant fluid and acidify with acetic acid. The 

 precipitate dissolves only partially, leaving a red residue. 



NOTES. i. The alkali converts the pigment into haematin, which is 

 precipitated with the earthy phosphates. 



2. Certain substances, such as cascara sagrada, rhubarb, senna and 

 santonin cause the urine to give a similar red precipitate when boiled with 

 alkali. But in these cases the precipitate dissolves completely in acetic acid. 



375. Schumm's spectroscopic test. Treat 50 cc. of the urine 

 with 5 cc. of glacial acetic acid and 50 cc. of ether. Shake thoroughly 

 in a separating funnel. Allow to stand and add a drop or two of 

 alcohol to obtain a separation of the layers. Run off the urinary 

 layer. To the ether add 5 cc. of water, shake and run off the water. 

 To the washed ether add ammonia and shake for half a minute, 

 cooling under the tap. The reaction must be markedly alkaline 

 after shaking. Run off the lower coloured layer into a tube, add 

 5 to 10 drops of ammonium sulphide solution and examine spectro- 

 scopically for the bands of haemochromogen. (Ex. 305.) 



376. Benzidine test. To a large " knife point " of benzidine 

 in a perfectly clean, dry test-tube add about 3 cc. of glacial acetic 

 acid and agitate for about a minute. Add an equal volume of 

 " 10 volumes " hydrogen peroxide. Mix and pour one-half into 

 another clean, dry test-tube. To one of the tubes add I cc. of the 



