342 Br. A. Holmes — Non-German Sources of Potash. 



surface. Over an area of 200,000 square yards sylvite has been 

 proved to a depth varying from 2 to 5 feet. The average content 

 of KC1 in this part of the deposit amounts to 80 per cent, while 

 locally the purer material exceeds 98 per cent of KC1. Small 

 quantities of NaCl are present, and also traces of MgCl 2 , bromine, 

 and iron oxides. Surrounding the sylvite and extending over an 

 area ten times as great, carnallite is found to a depth of 150 feet. 

 This is the greatest depth reached by the boreholes, and even near 

 the junction of the carnallite with the surrounding rock-salt the 

 lower surface of the former had not, in 1918, been reached, suggesting 

 a plug- or funnel-like mode of occurrence. The carnallite beds 

 average from 25 to 15 per cent of KC1 according to the depth, but it 

 is possible, without difficulty or special plant, to prepare for export 

 much richer material. The carnallite is exposed to the sun as it is 

 dug, and at the relatively high temperature normal to the district it 

 becomes unstable, and liquefies in its own water of crystallization. 

 From the solution so produced most of the KC1 is directly deposited, 

 leaving a mother - liquor which is concentrated with respect to 

 carnallite, but which is still unsaturated with respect to MgCl 3 . By 

 allowing this liquor to flow away, a high proportion of the MgCl 2 is 

 removed. The first effect of the evaporation of the liquor is the 

 redeposition of carnallite, and although it is stable in the presence of 

 MgCl 2 solution, it breaks down as before when the MgCl 3 flows away. 

 The process is allowed to continue on these lines until finally 

 a residue containing over 80 per cent of KC1 remains to be packed 

 for transport to the coast. 



The saline deposit as a whole displays an unusually complete 

 sequence, and is clearly the result of evaporation in an arm of the 

 Red Sea cut off permanently or intermittently by the volcanic hills 

 of the present coast. Associated phenomena, however, indicate that 

 volcanic agencies have also contributed to the development of the 

 deposit. A series of springs rises through the carnallite zone, varying 

 in temperature from 50° C. to 90° C. These consist essentially of 

 saturated solutions of MgCl 3 , with appreciable quantities of bromine 

 and small amounts of sodium, potassium, and iron. 1 At the north- 

 eastern corner of Dellol a deposit of "brimstone" has been found, 

 surrounded by a deep bed of " flowers of sulphur ". The latter mode 

 of occurrence points indubitably to condensation of the sulphur, 

 either directly from the gaseous state or from the interaction of 

 gaseous sulphur compounds. The hot springs, the sulphur deposit, 

 and the abundance of volcanic activity in the neighbourhood add 

 extraordinary interest to the area, and it is to be hoped that an 

 authoritative description and interpretation may soon be forthcoming. 



The southern part of the Piano del Sale has not yet been thoroughly 

 explored, and as it contains various focal points of depression there 

 is a reasonable possibility that other areas of potash salts still await 

 discovery. Political considerations are likely, however, to prevent 

 development in this direction, at least for the present, since the 



1 The springs are described in an Italian paper by M. Giua, of which an 

 English summary is published in the Journ. Soc. Cbem. Ind., vol. xxxvii, 

 p. R460, 1918. 



