CRYSTALLINE COMPONENTS 67 



EARLANDITE, Ca3(QH50,),.4H,0 



The third group of crystalline constituents differs completely from the calcium 

 oxalate and gypsum crystals. They were separated from fine and coarse samples from 

 St. 417, 7i"22'S, 16° 34' W, 1410 fathoms = 2580 m. consisting chiefly of quartz 

 grains, foraminifera, etc. The fine samples also contain a moderate number of pale 

 yellow to white nodules ^-ih mm. in diameter, with a warty surface, whilst the coarse 

 samples yielded some larger nodules up to 2 mm. in diameter and a few fragments up 

 to 3 mm. across, obviously portions of the crusts of still larger but hollow nodules 

 (Plate II A, fig. i). Of particular interest were a nodule attached by siliceous cement 

 to the wall of a specimen of the foraminifer Rhabdammina linearis, Brady (Plate II A, 

 fig. 2) and another nodule which had been incorporated with other mineral grains in the 

 tube of a marine worm. The discovery of these two specimens by Mr Earland places 

 entirely beyond doubt the fact that this third crystalline component is also of deep-sea 

 origin and has not resulted from accidental contamination of the sea-bottom samples. 

 Both large and small nodules are polycrystalline and very fine-grained < 10 * mm. 

 They vary in specific gravity from i-8o to 1-95 and the aggregate refractive index of 

 crushed nodules is 1-56. X-ray powder photographs of a nodule of sp. gr. i-8o and 

 another of sp. gr. 1-95 are identical (Plate II A, fig. 3) but quite different from powder 

 photographs of the tetragonal and monoclinic hydrates of calcium oxalate. Nevertheless 

 the nodules give a definite reaction for calcium, dissolve in dilute acid and decolorize 

 potassium permanganate solution. They must therefore be composed of a calcium salt 

 of an organic acid other than oxalic acid. Efforts were then made to establish the 

 identity of the nodules by comparison with other insoluble calcium salts of organic 

 acids known to exist in plant cells. Both calcium tartrate and calcium malate have been 

 recorded as plant constituents (A. Zimmerman, 1892) but powder photographs of both 

 artificially prepared salts are found to be quite different in pattern from the powder 

 photograph of the nodules from St. 417. Since citric acid is present in many fruit 

 juices Mr Hey suggested that calcium citrate, a very insoluble salt, should also be com- 

 pared. Powder photographs of the artificially prepared salt and the deep-sea nodules 

 are identical (Plate II A, fig. 3). Moreover, the specific gravity of the artificial salt is 

 1-951, i.e. identical with the highest observed specific gravity of the nodules and the 

 aggregate refractive index is the same for both, viz. 1-56. The artificial salt shows a 

 marked tendency to spherulitic formation, but the individual crystal plates are suf- 

 ficiently large to yield single crystal X-ray photographs. Since crystallographic and 

 optical data for calcium citrate are not recorded in the literature we hope to publish 

 measurements on single crystals at a later date. 



By the courtesy of Dr E. Hope the Dyson Perrins laboratory, Oxford, undertook the 

 microchemical analysis of the deep-sea nodules and obtained the results given in 

 Table III. 



Mr Hey also made residue determinations on two separate samples of nodules 

 and on artificially prepared calcium citrate. The chemical work confirms the X-ray 



