CH. XII.] ALBUMIN. 303 



structure of the kidney. In accidental albuminuria, the 

 protein is not passed by the kidney, but gains access to it 

 lower down in the urinary tract. It is generally accom- 

 panied by haemoglobinuria. 



For routine work the author uses the boiling test. In 

 cases of doubt the sulphosalicylic test is simple and reliable. 



For the method of estimating the albumin see Exs. 

 420,421. 



367. Boiling test. Filter the urine till it is clear. If it will 

 not filter clear, as when infected with bacteria, shake with kieselguhr 

 and filter again. If the urine be alkaline to litmus, make it faintly 

 acid by the cautious addition of i per cent, acetic acid. Fill a 

 narrow test-tube three parts full with the clear urine, incline it at an 

 angle and boil the upper layer by means of a very small flame. A 

 turbidity indicates either albumin or earthy phosphates (see note 

 2 to Ex. 28). Add one or two drops of strong acetic acid, boiling 

 after the addition of each drop. Any remaining turbidity indicates 

 the presence of albumin. 



368. Heller's test. Place about 3 cc. of pure nitric acid in a 

 narrow test-tube. Float about 3 cc. of filtered urine on the surface 

 of this, using a pipette to avoid mixing. A white ring at the junc- 

 tion of the fluids indicates the presence of albumin. 



NOTES. i . The white ring is due to the formation of metaprotein by the 

 action of the acid on the albumin, and the insolubility of the metaprotein in 

 the strong nitric acid (see Exs. 21 and 40). 



2. A coloured ring is usually produced owing to the oxidation of certain 

 urinary chromogens. 



3. In very concentrated urine, a white ring of urea nitrate may form. 

 It usually has very sharply denned borders. 



4. If the urine is very rich in urates, a precipitate of uric acid may form 

 at the junction of the fluids, or, more commonly, somewhat above the nitric 

 acid. Urea and uric acid are distinguished from albumin by the previous 

 dilution of the urine with two or three volumes of water. 



5. The presence of resinous substances in the urine of patients who have 

 been treated with balsams leads to the development of a white ring or cloud 

 that disappears on treatment with alcohol. 



6. Urine rich in albumose may give a white cloud that disappears on 

 warming. 



7. Urine that has been preserved by the addition of thymol gives a ring 

 of nitroso thymol or nitro thymol. The thymol can be removed by gentle 

 agitation with^petroleum ether. 



