1910.] 



Blood in Vertebrates and Invertebrates. 



607 



ill the capsule and the residue heated to dull redness. If, now, on 

 dissolving this residue in 5-8 c.c. of water, the solution was not clear, it was 

 filtered, the filtrate evaporated, and the residue again heated to dull redness, 

 then dissolved in not more than 5 c.c. of water and the solution filtered. 

 This solution, which contained only the carbonates of sodium and potassium, 

 was treated with hydrocldoric acid to convert them into the chlorides ; the 

 solution was now evaporated to dryness in a weighed platinum capsule, and 

 the weight of the chlorides of sodium and potassium determined. 



To determine the potassium the chlorides were dissolved in water ; to the 

 solution 3-5 c.c. of a 10-per-cent. solution of platiniim chloride were added, 

 and after the addition also of 3 c.c. of concentrated hydrochloric acid, the 

 mixture reduced almost to dryness in a porcelain evaporating dish on a 

 water bath. The residue was covered with 40 c.c. of absolute alcohol, the 

 mixture stirred for a few moments, and then allowed to stand under a bell 

 jar for an hour, at the end of which time 20 c.c. of ether were added, and a 

 further extraction of an hour was allowed. After decanting the alcohol-ether 

 mixture, a fresh mixture, consisting of 40 c.c. of alcohol and 20 c.c. of ether, 

 was added and allowed to extract for an hour. On decantation of this a 

 third supply was added, and the extraction continued for another hour. The 

 supernatant fluid, which was quite colourless, was also removed by 

 decantation ; the residue was then dried, and the platinum salt in it was 

 reduced to metallic platinum by heating it to 250° C. in a current of dry 

 hydrogen. On cooling, the salt was dissolved in water, then evaporated to 

 dryness, and once more subjected to reduction in dry hydrogen gas. This 

 latter procedure was adopted in order to ensure complete reduction of all 

 the platinum salt present. 



The weight of the platinum thus found, multiplied by the factor 0'40195, 

 gave the amount of potassium. This factor corresponds approximately to the 

 theoretical value of K in the formula K2PtCl6. 



The determination of the iron, copper (in Crustacean blood), calcium, 

 magnesium, and phosphoric acid was, except in cases to be mentioned 

 subsequently, made in the following manner : — To the weighed quantity of 

 the blood or serum held in a platinum dish about 2 grammes of pure sodic 

 carbonate were added ; the mixture, after being carefully stirred, was 

 evaporated to dryness, the residue carbonised, then extracted several times 

 with hot water, acidulated with hydrochloric acid, the remainder of the 

 residue completely incinerated, the ash extracted with hot dilute hydro- 

 chloric acid, the fluid filtered, and the filtrate added to the volume of the 

 united filtrates previously obtained. What remained undissolved was ferric 

 oxide (Fe203), which was weighed. Into the acid solution, when it contained 



