254 



THE BLOOD. 



[CH. X. 



for a while and fill up to the mark with boiled out distilled water. Vigorous 

 shaking of the fluid must be avoided. The solution should not be used for 24 

 hours. 



2. Acidified potassium chloride. To 1360 cc. of a cold saturated solution 

 of pure, recrystallised potassium chloride add 3-75 cc. of N. hydrochloric acid, 

 and make the volume up to 2 litres with distilled water. 



3. Soluble starch, i gram, of soluble starch is dissolved in 100 cc. of a 

 boiling solution of potassium chloride, saturated at room temperature. After 

 cooling the volume is made up to 100 cc. with distilled water. 



4. iodine. To 2 grams, of potassium iodide in a 100 cc. volumetric 



200 



flask add i to 2 cc. of a 2 per cent, solution of potassium iodate and a few cc. 

 of distilled water. Then add 5 cc. of o-i N. hydrochloric acid by means of a 

 pipette and make the volume up to 100 cc. with cold, recently boiled, distilled 

 water. 



5. Absorbing papers. A thick blotting paper 

 cut into pieces about 25 x 8 mm. The paper 

 used must be quite pure, and not yield any soluble 

 matter on extraction. 



6. An accurately graduated pipette to contain 

 o-i to 0-13 gram, of distilled water at 15 C. These 

 pipettes are best made from millimetre tubing and 

 should be engraved with the exact weight of water 

 they deliver. The weight of blood used is obtained 

 by multiplying the weight of water by i -06. If a 

 torsion balance (p. 388) is available the measure- 

 ment of the blood is simplified. 



7. A standard heating apparatus (see fig. 15, 

 p. 136). The pressure of gas and height of gauze 

 must be so arranged that 14 cc. of the acidified 

 potassium chloride solution are brought to the boil- 

 ing point in i minutes 5 sees. 



8. 50 cc. flask of " Duro " glass, with a 

 straight neck, so that a piece of thick walled rubber 

 tubing about 3 mm. thick, and about 5 cm in 

 length, can be slipped over the neck. A screw clip 



is fitted, so that the flask can be hermetically sealed. This is shewn in 

 fig. 3i. 



9. Apparatus for titration in an atmosphere of CO 2 . Owing to the 

 rapidity with which the cuprous chloride is oxidised it is necessary to exclude 

 air by means of an atmosphere of CO 2 . This is best accomplished by means 

 of the simple apparatus shewn in fig. 32. 



10. Cylinder of CO 2 , or a Kipp's generating apparatus charged with 

 pieces of marble and hydrochloric acid (i in 3). 



n. A steam oven for drying the paper. A large cork is transfixed with 

 a needle or pin, on which the clip that holds the paper can be suspended. 



Method. 



i. To obtain a measured amount of blood. 



Fig. 31. Flask fitted 

 for sugar estimation. 



A. By weighing with a torsion balance. 



