Human hæmoglobinuria may be the result of various pathological conditions, among which may be mentioned some infectious diseases, jaundice, burns, and the effects of many poisons, as well as the transfusion of sheep's blood. Intermittent hæmoglobinuria, which is attended with fever, is usually the result of cold acting upon predisposed persons. The color of the urine and of the coagulum, together with the absence of red corpuscles under the microscope, will distinguish urine of this character from others which are also coagulable by heat. Several methods are in use for the detection of albumen. Of these, boiling is perhaps the oldest and most generally employed, and if conducted with due care is a very delicate and useful test. The urine to be tested should be clear and slightly acid, when on boiling the albumen, if present, will be precipitated in whitish flocculi, more or less abundant according to the amount, or, if the quantity is very small, as a turbidity. The flocculi soon settle to the bottom of the tube when it cools, and the thickness of the deposit formed gives an approximation to a quantitative estimate. It is to the proportionate thickness of this deposit that the terms 30 or 50 per cent. of albumen are commonly but incorrectly applied. If the quantity is very small, it may not be distinctly perceptible until after cooling. If alkaline or very slightly acid urine is boiled, a deposit of phosphates will be thrown down which closely resembles that from albumen, while, on the other hand, the albumen remains undissolved unless in large amount. These deposits of phosphates differ a little in appearance from {36} an albuminous one, but in order to be accurate acetic or nitric acid should be added, drop by drop, to the hot urine, when the phosphates will be redissolved and the albumen, if present, precipitated. It is better, however, to add the acid cautiously to the point of slight acidity before boiling. A recent work[14] gives the following directions for this reaction, which is then "absolutely conclusive and surpassed in delicacy by no other:" "The urine is first made distinctly acid with some drops of acetic acid, and then about one-sixth of its volume of a concentrated solution of chloride of sodium or sulphate of sodium or magnesium added. If the urine contains albumen, a precipitate of coarser or finer flakes appears on boiling." This reaction may be used as a quantitative test by diluting and acidifying, if necessary, a known quantity of urine, washing the precipitate on a weighed filter, drying, and weighing the whole. [Footnote 14: _Die Lehre vom Harn_, Salkowski und Leube.]