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<br />DISTILLATION. After the sample has reached room temperature, <br />add 250 ml of H2O, a little at a time and with shaking at <br />first. Cool the sample and flask under running tap water. <br />Pipet 50.00 ml of standard N/10 acid (HC1) into a 500 ml <br />Erlenmeyer flask, add 3 drops of methyl red. <br />Pour down the side of the inclined, stationary Kjeldahl <br />flask, 100 ml of 458 (w/w) NaOH solution. Quickly drop in <br />a strip of litmus paper and a pinch of granulated zinc, and <br />with careful haste, insert the stopper into the flask. <br />Gently swirl the flask to mix the solution; ascertain that <br />the solution is basic, then mix well by swirling. <br />Turn on the burner and boil gently until half the solution <br />has been distilled into the standard acid. <br />TITRATION. Titrate the cool, excess acid with standard <br />N%10 base. <br />Report ~ N. _ (m mol HC1 - m mol NaO11) X 14.0067 X 1 <br />Y 100 sample wt. <br />2) Analysis of Cations in Soil for iron, potassium, sodium, <br />magnesium, zinc, and phosphorus by Atomic Absorption Spec- <br />trophotometry. <br />REAGENTS. Hydrochloric acid, HC1, concentrated. hydrofluo- <br />ric acid, HF, 488. <br />STANDARD SOLUTIONS. <br />suitable dilution of <br />element. <br />SAASPLE PREPARATION. <br />sample in a platinum <br />hours. Transfer the <br />beaker. <br />All standard solutions, are prepared by <br />the stock standard solutions for each <br />Ignite a 1.000 ± 0.005 g dried soil <br />or porcelain crucible at 900°C for two <br />ignited sample to a 100 ml Teflon <br />For samples expected to be High in alkaline cartlzs, treat <br />the sample with 10 ml of 1+l HC1 for 1 hour at GO-80°C. <br />Decant the supernatant, which contains most of the alkaline <br />earth metals, into a 250-m1 volumetric flask, and retain. <br />Treat the residue as directed below. <br />For samples not expected to be high in alkaline earths and <br />for the residue of the 1+1 HC1 extraction described above, <br />dissolve by adding 10 ml of HF and 10 ml of ?IC1 and evapo- <br />rating to dryness. Repeat tl~e addition of HF and HCL and <br />evaporation to dryness. Add 5 ml of HC1 and evaporate to <br />dryness, and dissolve tl~e residue in a minimum amount of <br />HC1. Transfer the solution to a 250-m1 volumetric flask, <br />combining it with the acid extract for liiyh alkaline eart}: <br />Samples, and dilute to volume so that the Einal acid <br />-2- <br />