72 



MARINE BOTTOM SAMPLES OF LAST CRUISE OF CARNEGIE 



the crystal lattice of the mineral; and (3) the amount of 

 water lost at temperatures below the break in the curve, 

 which indicates the amounts of absorbed water and, thus, 

 something of the crystal structure. 



In figure 6 are given the dehydration curves for kao- 

 linite and halloysite, taken from a paper by Ross and 

 Kerr (1933), and for glauconite and a Mississippi ben- 

 tonite containing montmorillonite, taken from Nutting's 

 report. It will be noticed that the amount of water lost 

 by halloysite below the break in the curves is much 

 greater than in kaolinite, and that the loss in the benton- 

 ite is about twice that of halloysite, corresponding with 

 the well-known ability of bentonite to absorb large quan- 

 tities of water. There is a sharp break in the halloysite 

 curve between 420° and 500°, whereas the even sharper 

 break in kaolinite occurs at temperatures close to 500°. 

 About 10 per cent of water is lost between these temper- 

 atures. In the bentonite curve there is a much more 

 gradual break between 500° and 600° in which only about 

 3 per cent of water is lost. 



The breaks in the curves for samples 34, 69, 72, 73, 

 and 77 begin at about 400° to 500°, but the amount of 

 water lost is, in every case, about 3 per cent, the same 

 as in bentonite, and the breaks are of the same general 

 character, being neither as abrupt nor as large as those 



of the halloysite or kaolinite curves. There is one im- 

 portant difference, however, between the dehydration 

 curves for the samples mentioned and that of montmo- 

 rillonite, as exemplified by the Mississippi bentonite. 

 This is in the amount of water lost below 400°, which in 

 no case exceeds 6 per cent, and for samples 69, 72, and 

 77 is about 3 per cent, as contrasted with the loss of 

 about 11 per cent in bentonite. In terms of crystal 

 structure, this means that in the lattice packages of the 

 mineral involved the atomic layers cannot be stretched 

 apart as widely by the absorption of water as in mont- 

 morillonite. 



Professor W. P. Kelley, who has seen these curves, 

 states in a personal communication that they are very 

 similar to those obtained in his laboratory for certain 

 California soils previously mentioned which contain a 

 clay mineral similar to, but not identical with, beidel- 

 lite. The dehydration curves thus corroborate the con- 

 clusion that the chief clay mineral in Pacific deep-sea 

 clays is beidellite-like in type. 



The break in the curve of sample 31 between 550° 

 and 600° is owing to the presence of calcium carbonate. 

 Below 500°, however, the curve is quite different from 

 those of the other clays and probably indicates a more 

 complex mineralogical composition. 



MECHANICAL ANALYSES 



Pipette Analyses 



Method 



Fourteen samples, including six Globigerina oozes, 

 six red clays from the northeast Pacific, and two south 

 Pacific clays, were mechanically analyzed by the pipette 

 method, first introduced by Robinson (1922), Jennings, 

 Thomas, and Gardner (1922), and Krauss (1925). This 

 has been adopted as the international method for soil 

 analyses, and has been used on a great many sediments 

 from the Baltic Sea by Gripenberg (1934). The proce- 

 dure of analysis followed closely that outlined by Krum- 

 bein (1932) as modified by Rittenhouse (1933). The sam- 

 ple to be analyzed, usually weighing from 10 to 20 grams 

 in the moist condition, was carefully quartered, and a 

 part of 3 to 6 grams was placed in an 8-ounce sterilizer 

 bottle, which contained about 3 ounces of water. The 

 bottle was shaken for a period of 8 to 24 hours, after 

 which the material was poured through a Sieve with 

 meshes of about 0.07 mm. The residue remaining on 

 the sieve was washed until clean, dried on a sand bath, 

 and separated into fractions by hand sieving with the use 

 of a series of standard sieves for mechanical analyses. 

 The part which had passed through the sieve was washed 

 pearly free of salt by repeated centrifuging and, after a 

 period of further shaking in the sterilizer bottles, was 

 allowed to stand overnight to see if flocculation would 

 occur. With red clays washing and shaking were suffi- 

 cient often to bring about apparent dispersion. Three 

 drops of 28 per cent ammonia were added to the sam- 

 ples which were found to have flocculated on standing 

 overnight, and shaking was continued. In some cases 

 further washing by itself brought about dispersion, 

 whereas even after repeated washing and shaking with 

 ammonia, certain Globigerina oozes, notably samples 

 22, 27, and 44 could not be dispersed. In these cases no 

 attempt was made to effect satisfactory dispersion by 



other means or with other peptizing agents, and further 

 mechanical analysis was abandoned. Although such so- 

 dium salts as the phosphate, citrate, oxalate, and car- 

 bonate are said to effect a greater degree of dispersion 

 than ammonia, the latter was used, principally because 

 the colloidal fractions of the samples analyzed were 

 later to be utilized for chemical and X-ray analyses. 

 The ammonia was probably nearly completely driven off 

 during drying. 



When a sample was apparently dispersed, as evi- 

 denced by the absence of any fluffy, flocculated mass at 

 the bottom of the bottle after standing, as well as by the 

 appearance of the material under microscope, it was 

 transferred to a half-liter Pyrex graduate and the vol- 

 ume of the suspension was brought up to 500 cc. The 

 graduate was then placed in a water bath, either in a 

 dark constant -temperature room or, in the case of the 

 first analyses, merely away from direct light. One or 

 two pipette samples were withdrawn while the suspension 

 was being thoroughly shaken, and these were used as a 

 measure of the weight of material in suspension. Sub- 

 sequent samples were withdrawn at increasing time in- 

 tervals, with 10 and 20 cc automatic pipettes, from 

 measured depths in the suspension, usually 10 or 5 cm. 

 The pipetted samples were first dried on a water bath 

 and then at 105° for several hours, or were dried on a 

 sand bath. 



The pipette method rests on the assumption that in a 

 dilute suspension, each particle sinks to the bottom with 

 its own particular velocity independently of other parti- 

 cles. If a thoroughly shaken suspension in which the par- 

 ticles are uniformly distributed is set at rest, all parti- 

 cles having a settling velocity greater than h/t will have 

 settled below the depth h at the end of the interval of 

 time tj whereas all particles of lesser velocity will re- 

 tain their initial concentration at this depth, since each 

 one of them will have settled below the surface through 

 a distance smaller than h. Consequently, if a thin 



