ANALYTICAL SEARCH FOR METALS IN TORTUGAS MARINE 



ORGANISMS. 



BY ALEXANDER H. PHILLIPS. 



INTRODUCTION. 



The problem upon which it is hoped that these analyses will cast 

 some light was stated in Year Book No. 14, page 193, of the Carnegie 

 Institution of Washington. A large number of specimens were col- 

 lected and, while only a few of them have been analyzed for metals, the 

 results justify the present publication, leaving the discussion to some 

 future time when the analyses of all the samples or specimens collected, 

 as well as others from various localities, might be included. 



The specimens were dried in the air-bath at 110 C., were ground, and 

 bottled in bottles with tight-fitting stoppers. Some specimens slowly 

 decomposed at 110 C. and constantly lost weight; in such cases the 

 specimens were heated in the bath for 8 hours and then bottled as if 

 dry. The metals determined were iron, manganese, zinc, copper, and 

 lead. For the determination of zinc, copper, and lead, when the dried 

 material was sufficient, 20 grams were used as a sample; when it was not 

 possible, through lack of material, to use 20 grams, the results, as tabu- 

 lated for convenience of comparison, are all calculated to 20 grams. 



METHOD. 



The method of analysis followed is that advised by the U. S. Depart- 

 ment of Agriculture, Bureau of Chemistry, Bulletin No. 107 (revised), 

 with slight modifications, as tin was not sought. The sample was 

 incinerated in a muffle at a low red heat, not high enough to fuse the 

 chlorides. After solution of the ash in HC1 and evaporation to 

 dryness, sulphides were precipitated in a hydrochloric-acid solution. 

 They were then dissolved in HN0 3 , when copper and lead, if any, were 

 determined electrolytically in the nitric-acid solution. Iron and 

 phosphoric acid were separated from zinc in the filtrate from the 

 sulphides by the basic-acetate method, when the zinc was precipitated 

 as a sulphide in an acetic-acid solution and weighed as ZnO. If this 

 zinc oxide was found to be impure it was dissolved in hydrochloric acid, 

 filtered, and the filtrate was boiled with an excess of NaOH in platinum, 



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