Important Source of Error in Heller's Test. 



5 



may be precipitated in the form of glittering nitrate crystals ; but 

 dilution of the urine prevents these effects. 



In the course of our investigation of another problem, an ad- 

 ditional source of error has been found in urines preserved with 

 thymol in any of the usual ways. If Heller's test is applied to 

 such urine after filtration, a ring will invariably appear even in the 

 absence of protein. The ring is most marked, all other things 

 being equal, in urines that have been treated with a solution of 

 thymol, although it is very conspicuous in urines that have been 

 preserved with powdered thymol. 



The characteristics of this ring may be briefly stated as fol- 

 lows : A few seconds after the urine has been carefully poured 

 upon the acid, there forms, precisely on the line of junction, a 

 grayish white ring about 0.5 mm. high, resembling the albumin 

 ring given by a faint trace of albumin, and gradually becoming 

 more and more distinct, until, in some urines under conditions to 

 be mentioned later, it presents the appearance of a heavy thick 

 precipitate, the height of which increases continuously and renders 

 the lower portion of the urine completely opaque. At this stage 

 the color is somewhat different from that of a protein ring, in that 

 it is more yellowish. Below the ring there is a greenish zone ex- 

 tending somewhat into the acid ; above it, a reddish zone smaller 

 than the former and more contracted. The white ring is seen 

 best in daylight reflected from a dark background, the color rings 

 are seen best if the test-tube is held against a white surface. 



On slightly disturbing the layers of urine and acid the ring, if 

 a deHcate one, disappears but reappears immediately. These ef- 

 fects can be obtained a few times in the same mixture. A heavy 

 ring, however, will not completely disappear on slightly shaking 

 but will gradually widen and extend into the upper urinary layer ; 

 and it depends on the volume-relation between urine and acid 

 whether complete mixing will remove the precipitate. On thor- 

 oughly shaking an excess of acid with little urine, a clear yellow 

 solution results. If an excess of urine has been used, the mixture 

 will not clear, but will remain turbid. Warming the mixture 

 will not prevent the formation of this ring, nor will it clear the 

 liquid, but, if anything, will make the reaction more distinct ; nor 

 has dilution of the urine with three to four times its volume of water 

 any marked effect. 



