HEMOGLOBIN ESTIMATION 



173 



N/io HC1, haematin hydrochlorate is produced, which gives a brownish- 

 yellow color. In the standard tube, which is sealed, a dilution repre- 

 senting i% of normal blood is used. To apply this test, pour in N/io 

 HC1 to the mark 10 on the scale of the graduated tube. Add to this 20 

 cubic millimeters of the blood to be examined, drawn up by the capillary 

 pipette provided. So soon as the mixture assumes a clear bright dark 

 brown color, add water drop by drop until the color of the tubes matches. 

 The reading of the height of the aqueous dilution on the scale gives 

 the Hb. reading. The tubes are encased in a 

 vulcanite frame with rectangular apertures. 

 This gives the same optical impression as 

 would planoparallel glass sides. 



The most accurate readings are obtained with ar- 

 tificial light in a dark room but almost as satisfactory 

 comparisons can be obtained with natural light from 

 a window. It is advisable to turn the ruled side 

 around so that one may match colors without being 

 influenced in his determination by the scale. 



The apparatus must be kept in a dark place as 

 strong light will change the color of the standard 

 tube. It is recommended that the N/io HC1 be 

 preserved with chloroform. 



Tallquist's Haemoglobin Scale. This is 

 a small book of specially prepared filter-pa- 

 per with a color-scale plate of ten shades of 

 blood colors. These are so tinted as to match 

 blood taken up on a piece of the filter-paper 

 and are graded from 10 to 100. So soon as the 

 blood on the filter-paper has lost its humid 

 gloss, the comparison should be made. This 

 is best done by shifting the blood-stained 

 piece of filter-paper suddenly from one to the 

 other of the holes cut in each shade -the 

 piece of filter-paper being underneath the color 



plate. At least a square centimeter of the filter paper should be stained 

 by the blood. Daylight coming from a window to the rear or at the side 

 should be used in making the comparison. The error with this method 

 is probably not over 10% after a little experience. If the colored plate 

 is not kept in the dark, the tints tend to fade. 



FIG. 51. Sahli's haemo- 

 globinometer. (Greene.} 



