PRODUCTION OF BORAX FROM LAKE BRINES

                                                   
A minor but significant proportion of North American borax production is from the brine of searle's lake,also situated in the mojave desert...This is a dry lake of about 34 square miles in area and has saturated brine[urea 35% solids] to within a few inches of the surface filling channels and voids  which occupy 40-50% of the cross-section effectively about 120 feeet thick but in two main layers..The brine is rich in soda,potash,sulphate and chloride but contains about 1.5-2% of B2O3[Equivalent to 5% Na2B4O7.10H2O]..In the main process operated by north american chemical CO in trona,the upper layer brine is pumped from wells and concentrated by evaporation ..Rapid cooling precipitates potassium chloride which is a valuable product with respect to borax which is
recovered
above the transition temperature as the pentahydrate and then re-crystallized to the commercial product..An alternative method used by American potash involves acidification of the alkaline lower-layer brine with flue gas C02..Sodium carbonate is thereby converted into sodium bicarbonate,which precipitates because of its lower solubility..At the same time the NA2B203 ratio of the liquors is altered from the 1:2 of borax to 1:5 of sodium pentaborate  at which the water solubility with respect to B203 is much greater.When further quantities of lake brine are added,The ph and the ratio are restored to their original values after which the less soluble borax is crystallized out upon refrigerated cooling..