PROTEIDS. 745 



proper amount of acid is now added to the urine, so as to prevent any 

 mistake caused by the presence of earthy phosphates, and to give a better 

 and more fiocculent precipitate of the proteid. If acetic acid is used 

 for this, then add 1-3 drops of a 25 per cent acid to each 10 cc. of the 

 urine and boil after the addition of each drop. On using nitric acid, 

 add 1-2 drops of the 25 per cent acid to each cubic centimeter of the 

 boiling-hot urine. 



On using acetic acid, when the quantity of proteid is very small, 

 and especially when the urine was originally alkaline, the proteid may 

 sometimes remain in solution on the addition of the above quantity of 

 acid. If, on the contrary, less acid is added, the precipitate of calcium 

 phosphate, which forms in amphoteric or faintly acid, urines, is liable 

 not to dissolve completely, and this may cause it to be mistaken for a 

 proteid precipitate. If nitric acid is used for the heat test, the fact must 

 not be overlooked that after the addition of only a little acid a combina- 

 tion between it and the proteid is formed which is soluble on boiling and 

 which is only precipitated by an excess of the acid. On this account the 

 large quantity of nitric acid, as suggested above, must be added, but in this 

 case a small part of the proteid is liable to be dissolved by the excess of 

 the nitric acid. When the acid is added after boiling, which is absolutely 

 necessary, the liability of a mistake is not so great. It is on these grounds 

 that the heat test, although it gives very good results in the hands of 

 experts, is not recommended to physicians as a positive test for proteid. 



A confounding with mucin, when this body occurs in the urine, is 

 easily prevented in the heat test with acetic acid by acidifying another 

 portion with acetic acid at the ordinary temperature. Mucin and 

 nucleoalbumin substances similar to mucin are hereby precipitated. If 

 in the performance of the heat and nitric-acid test a precipitate first 

 appears on cooling or is strikingly increased, then this shows the presence 

 of proteoses in the urine, either alone or mixed with coagulable proteid. 

 In this case a further investigation is necessary (see below). In a urine 

 rich in urates a precipitate consisting of uric acid separates on cooling. 

 This precipitate is colored and granular, and is hardly to be mistaken 

 for a proteose or proteid precipitate. 



HELLER'S test is performed as follows (see page 98) : The urine is very 

 carefully floated on the surface of nitric acid in a test-tube. The presence 

 of proteid is shown by a white ring between the two liquids. With this 

 test a red or reddish-violet transparent ring is always obtained with normal 

 urine: it depends upon the indigo coloring-matters and can hardly be 

 mistaken for the white or whitish proteid ring, and this last must not be 

 mistaken for the ring produced by bile-pigments. In a urine rich in 

 urates another complication may occur, due to the formation of a ring 

 produced by the precipitation of uric acid. The uric-acid ring does 

 not lie, like the proteid ring, between the two liquids, but somewhat 

 higher. For this reason two simultaneous rings may exist in urines 

 which are rich in urates and do not contain very much proteid. The 

 disturbance caused by uric acid is easily prevented by diluting the urine 

 with 1-2 vols. of water before performing the test. The uric acid now 

 remains in solution, and the delicacy of HELLER'S test is so great that after 

 dilution only in the presence of insignificant traces of proteid does this 

 test give negative results. In a urine very rich in urea a ring-like separa- 

 tion of urea nitrate may also appear. This ring consists of shining 



