roMl'LKTK \N.\I.YSIS. f) 1 



ing 1 gram of the sample with hydrofluoric and Bolphuric acids in a large covered 



platinum crucible. After boiling live minutes the solution is cautiously diluted and 

 it once titrated with potassium permanganate. 



1'oTASSIl M \\l>So|>[tM 0\ID. ! K..O. N;| I > 



( )ne-half gram of the very finely ground powder is mixeil with its o\vn weight of 

 pure ammonium ehlorid, and ihe two thoroughly ground together. About I grains 

 of pure calcic carbonate is added, and the grinding continued until an intimate mix- 

 ture is made. This mixture is t ransf erred to a .1 . Lawrence Smith tubular crucible " 

 and the mortar rinsed with a little extra calcic carbonate. The crucible is capped 

 mid placed in a fire-clay furnace and heated for about ten minutes by a low (lame. 

 As soon as no more odor of ammonia is perceptible it is heated by the full heat of 

 two r.unsen burners for three-quarters of an hour. After cooling, the sinten-d ma-s 

 usually detaches from the crucible but it maybe loosened with hot water. The 

 mass is transferred to a platinum dish, and digested with hot water until completely 

 disintegrated. The solution is filtered into a beaker and the residue washed, a few 

 drops of ammonia and ten of a saturated solution of ammonia carbonate added, the 

 solution filtered into a platinum dish, and the residue \\ashed thoroughly. Tin- 

 filtrate is evaporated to dryness, and the residue heated at a dull red heat until the 

 ammonia salts are expelled. After cooling, the residue is taken up with a little 

 water, and a few drops of ammonia and ammonic carbonate added to make sure that 

 all the calcium has been precipitated. The solution is filtered on a small filter into 

 a weighed platinum dish, and the precipitate and paper washed with hot water. A 

 few drops of dilute hydrochloric acid are added and the clear solution evaporated to 

 dryness. The ammonia salts are then expelled by very careful heating to a dull red 

 heat, and weighed as potassium and sodium ehlorid (KCl-f NaCl). 



The mixed salts are dissolved in water and an excess of platinic ehlorid added to 

 the solution. After evaporating nearly to dryness on a steam bath, 20 cc of alcohol 

 is added and allowed to stand 'one hour. The precipitate is filtered on a weighed 

 Gooch crucible, washed with alcohol, dried at a low heat in an air bath, and 

 weighed as potassium platinic ehlorid (K 2 PtCl 6 ), which multiplied by 0.1940 gives 

 potassium ehlorid (KC1). 



WATER. 



For the determination of water, the ordinary method of loss on ignition is not 

 depended upon except in cases in which it is quite certain that carbon dio.xid and 

 oxidizable or reducible matter are absent. A sample of about 2 grams of the air- 

 dried powdered material is w r eighed into a platinum boat, which is placed inside a 

 hard j;lass combustion tube and strongly ignited in a current of dry air. The expelled 

 water is collected in a sulphuric acid weighing tube, which is connected by a very 

 short piece of rubber tubing to the drawn-out end of the combustion tube. 



B. Substances mainly soluble in hydrocldor><- <"!,/. 



In the cases of limestones and dolomites which contain less than 1<> percent of 

 insoluble matter the weighed sample is treated with dilute hydrochloric acid, and 

 the solution, after the filtration of the insoluble residue, is treated exactly as under 

 A, "substances mainly soluble in hydrochloric acid." Whether or not the insolu- 

 ble residue will require fusion and separate analysis will depend upon the ohjY. 

 the analysis. Calcareous clays, which are' largely insoluble, are best treated as 

 under A, and fused at once. 



a Bui. U. S. Geological Survey 176; 97. 



