98 Analytical Search for Metals in 



constant weight, and the amounts of all the metals, reported in the 

 table above, are in each case expressed in grams per 20-gram sample. 

 The four metals sought occur in all the samples analyzed, but not 

 in as large amounts as in those forms where it is possible to separate 

 the soft tissues from the calcareous skeleton. In some of the present 

 material the calcareous skeleton was by far the larger part, by weight, 

 of the sample taken for analysis, thus reducing the amount of each 

 metal reported in the 20-gram sample, as there is no doubt that the 

 metals here reported are associated to a much greater extent with the 

 soft tissues than with the calcareous skeleton. 



From a consideration of the amounts of each metal reported in the 

 various organisms, there seems to be no ratio of occurrence or quanti- 

 tative relation of one to the other, but zinc is present in larger amounts 

 than copper. 



Sample No. 620-a-4 was composed of the soft parts of a number 

 of fresh-water mussels taken from the Millstone River east of Prince- 

 ton, at a point where all the water of the river is collected from a low, 

 level, sandy area far removed from any possible metallic veins. It 

 is interesting to note that this fresh-water form collects both copper 

 and zinc from such a natural water and in about the same amounts 

 as do the salt-water organisms. This may be true of other fresh- 

 water forms, but as yet this sample of Unio is the only one analyzed. 

 Iron and m.anganese in this case were not determined, as it was diffi- 

 cult to completely eliminate the silt contained in the intestines, and 

 as this silt would contain both iron and manganese, their determina- 

 tion under the circumstances would be of no interest. 



In the note'' A possible source of vanadium in sedimentary rocks''^ 

 it was stated that the conditions for the fixation of these small quanti- 

 ties of metal in the mud and slime at the bottom of the shallows and 

 lagoons are ideal, about the Tortugas at least, as the constant libera- 

 tion of hydrogen sulphide by the mud in the slightly alkaline sea- 

 water would precipitate all four of the above metals as sulphides, 

 even though they were present in very small quantities. 



To test this, the sample No. 615-A-l was analyzed for these 

 metals. The sample consists of a mud collected in the shallow lagoon 

 of the Marquesas, Florida, and taken by means of a special sampling 

 apparatus at a depth of 2 feet below the surface of the mud. The 

 results of this analysis are shown in the table. It is not surprising to 

 find iron and manganese, but zinc and copper are both present and 

 in larger quantities than the analyses show them to be present in 

 the organisms; therefore these metals are concentrated in this bottom 

 mud. Unfortunately, no other samples of muds were taken and the 

 extent of concentration of copper and zinc can not be determined at 

 present. 



> Amer. Jour. Sci., vol. xlvi, p. 471. 



