ELECTROLYTE CONTENT OF SEA URCHIN EGG. 169 



Magnesium. The filtrate from the above proceedure was then 

 made strongly alkaline with concentrated NH 4 OH, and an excess 

 of a solution of KoHPO 4 added, the solution allowed to stand 

 overnight, the precipitate filtered off on ashless filter paper, 

 washed with dilute NH 4 OH, ignited strongly, and weighed as 

 Mg 2 P 2 7 . 



Sodium. The filtrate from the above procedures was then 

 concentrated on a water bath to about 3 cc., made alkaline to 

 phenolphthalein with sodium free 10 per cent. KOH, 10 cc. of 

 potassium pyroantimonate reagent added and the procedure 

 further carried out as recommended by Kramer and Gittlemann 

 (i). Sodium cannot be determined directly in the presence of 

 fairly large amounts of Ca or Mg because these two elements are 

 precipitated by the pyroantimonate reagent and may be titrated 

 as sodium. 



Potassium. 2 cc. samples from the original filtrate were 

 analysed for potassium by the method of Kramer and Tisdall (2). 



Iron was estimated colorimetrically by the method of W. S. 

 Allen, using salicylic acid to develop the color as described by 

 Scott (3). 



Sulphate determined as BaSO4 following hot BaCl 2 pre- 

 cipitation. 



Chlorides were titrated using the Fr. Mohr method. 



Total Phosphorus and Lipoid Phosphorus was determined by 

 the Benedict-Theis method (4) modified for egg analysis as 

 described by Page (5). 



Nitrates were estimated by the phenolsulphonic acid method 

 ordinarily used in w T ater analysis. 



The above analyses were then carried out on filtrates prepared 

 as follows: Samples of one million eggs were centrifuged to 

 remove as much sea water as possible, made up to a 3 cc. mark on 

 the centrifuge tube with distilled water, 3 cc. more distilled water 

 added and the tube vigorously shaken to cytolyse the eggs. 

 After standing 15 minutes 4 cc. of 20 per cent, trichloroacetic 

 acid was added and approximately 0.2 grams of prepared bone 

 black, 1 again shaken and allowed to stand 15 minutes. The 



1 Commercial bone black boiled with HC1, thrown onto a Biichner filter and 

 washed until the nitrate was chloride free. 



