276-278] Details of the Analysis 165 



from the lime, which will be of considerable bulk, to a weighed 

 platinum dish 3 inches in diameter, and evaporate over a rose 

 burner turned down so low that ebullition does not quite take 

 place. When all the liquid has been boiled down to a very 

 small bulk, add 5 c.c. of strong HC1, and finish by evaporating to 

 dryness on the water bath. Next place on an Argand, and ignite 

 at a low temperature so as to drive off the ammonium salts. 

 This ignition will take two or three hours. When all fuming 

 ceases, heat to dull redness in the Bunsen flame for about half- 

 a-minute, cool in a desiccator, and weigh. The contents of the 

 dish are MgO, KC1, and NaCl. 



276. Magnesia. — Dissolve the weighed residue in hot 

 water and filter rapidly, washing with hot water. Dry the pre- 

 cipitate, ignite, and weigh as MgO. 



277. Potash. — Add 5 c.c. of platinum chloride solution, 

 evaporate on the water bath, and estimate the potash exactly 

 as in paragraphs 33-36. 



278. Soda. — This, as stated in the table, is calculated 

 by difference. This is done as follows : Calculate the K 2 PtCl 6 

 obtained in the last operation as percentage of the total weight 

 of soil taken. This multiplied by '193 gives percentage of 

 K 2 in the soil. 



Percentage of K 2 x 1*585 gives percentage of KC1. 

 Add the percentage of KC1 to that of magnesia, and subtract 

 from the percentage of alkaline chlorides and magnesia. The 

 result is the percentage of NaCl. Multiply the percentage of 

 NaCl by -53, and the result will be the percentage of Na 2 in 

 the soil. 



