42 CHEMICAL PHYSIOLOGY. 



Withdraw the cloth by means of the thread. Observe the 

 coloured fluid spectroscopically. 



(c.) Boil some of the extract with hydrochloric acid, and 

 add potassic ferrocyanide ; a blue colour indicates the pre- 

 sence of iron. 



(d.) Use the stain for the hsemin test, doing the test in a, 

 watch-glass (Lesson V., 5). 



AMOUNT OF HAEMOGLOBIN IN BLOOD. 



7. Colorimetric Method (Hoppe-Seyler's Method). A standard 

 solution of pure haemoglobin diluted to a known strength is 

 used, and with this is compared the tint of the blood diluted 

 with a known volume of distilled water. 



(a.) The demonstrator will prepare a standard solution of 

 haemoglobin of known strength. 



(b.) Spread a sheet of white paper on a table in a good 

 light opposite a window, and on it place two hsematino- 

 meters side by side (Fig. 6, D). See that they are water- 

 tight. If not, anoint the edges of the glass plates with 

 vaseline to make them water-tight. 



J;.) Take 10 cc. of the standard solution of haemoglobin 

 dilute it with 50 cc. of water, and place it in one of the 

 hsematinometer s . 



(d.) Weigh 5 grammes of the blood to be investigated, 

 and dilute it with water exactly to 100 cc. 



(e.) Place 10 cc. of this deeper tinted blood (d.) into the 

 second hsematinometer. 



(/) Fill an accurately graduated burette with distilled 

 water, place it over the second hsernatinometer (e.\ and 

 dilute the blood in it until it has precisely the same tint as 

 the standard solution in the other haematinometer. Note 

 the amount of water added. The two solutions must now 

 contain the same amount of hsemoglobin. 



Example (Hoppe-Seyler). 20 '186 grms. of detibrinated blood were 

 diluted with water to 400 cc. To the 10 cc. of this placed in a hsematino- 



