Journal - South African Institute of Mining and Metallurgy . ompound, such as CaO, inexpressing the alkali present, while it can at oncebe translated into terms of percentage of CaO orNaOH by multiplying by the equivalent weightof either unit = -0028% CaO = -056 lb. CaO per ton.„ -0056% KOH =T12 1b. KOH „„ -0040% NaOH = 0^0 lb. NaOH „•0065% KCN =13 lb. KCN „ • see this Journal Vol. v., April, 1905, p. 253; also voL viii.,pp. 37, 124 and 206. 296 The Journal of The Chemical^ Metallurgical cud Minimi Society of South Africa. April 1908 A saturated solution of lime La water has analkal
Journal - South African Institute of Mining and Metallurgy . ompound, such as CaO, inexpressing the alkali present, while it can at oncebe translated into terms of percentage of CaO orNaOH by multiplying by the equivalent weightof either unit = -0028% CaO = -056 lb. CaO per ton.„ -0056% KOH =T12 1b. KOH „„ -0040% NaOH = 0^0 lb. NaOH „•0065% KCN =13 lb. KCN „ • see this Journal Vol. v., April, 1905, p. 253; also voL viii.,pp. 37, 124 and 206. 296 The Journal of The Chemical^ Metallurgical cud Minimi Society of South Africa. April 1908 A saturated solution of lime La water has analkalinity of about 45. In a cyanide solution of known percentageKCN and alkalinity estimated by above Standard,the protective alkali in pounds CaO per ton,(.?an be calculated by the formula :— ?OoCxi - 8?()£ — pounds CaO jut ton,where a = alkalinity b) above standard, and k =percentage In daily work the solution man takes samplesof 20 , adds 2 or .5 drops of 1\ phenol-phthalein solution, and titrates with J 5 sulphuric FIG. Fir:. IT. April 1908 A. McA. Johnston The Laboratory: Its Economic Value. •_!>; acid. Each truth of a cubic centimetre of acidused represents one unit of alkalinity. When the protective alkali value is required in poundslime per t<»ns it is read from a table calculatedfrom tin formula above given. Synthetic testshave shown that this method, while not by anymeans strictly accurate in the presence of doublezinc cyanide, is liable to no greater errors thanthe methods based on titration after precipitationwith silver nit rati-. Noli /I . Preparation of Standard SulphuricAcid. Strong acid is diluted to give a stocksolution of medium strength, slightly greater than•IN. Exactly 100 of this is diluted to2,000 , and the I1.,S04 in a sample of thisdiluted acid is estimated gravimetrically with thegreatest care. If, for instance, it proves to be0*2055 X, we must then dilute 100 of thestock acid up to 2,000 and add 55
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