632 APPENDIX 



carbonate are fused as directed in Fresenius' "Quantitative Analysis," 

 page 426, and by Hillebrand in Bulletin 305 of the United States Geo- 

 logical Survey, where an illustration of the apparatus is given. The 

 fused mass is transferred to a porcelain dish, slacked with hot water, 

 finely ground with an agate pestle and transferred to a filter. After 

 washing with about 600 cc. hot water, the filtrate and washings are run to 

 dryness in a Jena beaker, taken up with hot water and again filtered, 

 acidified with hydrochloric acid, concentrated to about 10 cc., and i^ cc. 

 of a platinum chlorid solution (10 cc. containing i g. platinum) added. 

 This is then evaporated to a sirupy consistency, taken up and washed 

 about fifteen times with 80 per cent alcohol, three times with ammonium 

 chlorid solution, and again fifteen times with alcohol. The precipitate 

 is then washed through the filter with hot water into a platinum dish, 

 evaporated on the steam bath to dryness and heated in an air .oven at 

 110 C. for an hour, cooled in a desiccator, and weighed. Duplicate 

 samples should not differ more than 1.5 mg. in the final weight. 



A correction must be made for the amount of potassium in the reagents 

 which is found by making a blank determination, using no soil. 



(Ammonium chlorid solution is made by dissolving 200 g. NH 4 C1 in 

 1000 cc. water and saturating with K 2 PtCl 6 .) 



Calcium. Decompose 2 g. of soil (less if high in calcium) by heating 

 with 6 to 8 g. of sodium peroxid in an iron crucible ; transfer with water, 

 acidify with hydrochloric acid, evaporate to dryness ; and continue heat- 

 ing for about an hour, on the steam bath, to dehydrate the silica. Digest 

 the residue with hydrochloric acid on the steam bath until all that will 

 has gone into solution (about ten minutes will usually suffice) ; filter, and 

 wash free from chlorids with hot water. Bring the filtrate and washings 

 to about 150 cc. ; add .5 g. ammonium persulfate, heat to boiling; and 

 add ammonia in excess to precipitate iron, aluminum, phosphorus, and 

 manganese. After boiling about five minutes, filter while still boiling hot, 

 and wash with hot water till practically free from chlorids ; acidify with 

 hydrochloric acid, evaporate to about 100 cc., add i cc. of a 6 per cent 

 solution of ferric chlorid and about .5 g. of ammonium persulfate ; heat 

 to boiling, precipitate with ammonia in decided excess, boil for several 

 minutes ; then filter and wash as before. Bring the filtrate and washings 

 to a volume of about 150 cc. ; boil, and to the boiling solution add slowly, 

 and with constant stirring, enough concentrated ammonium oxalate 

 (5 to 10 cc.) to precipitate the calcium and to change the magnesium to 

 the oxalate. Digest for an hour or more on the steam bath, care being 

 taken that the volume does not go below 75 cc. ; filter, and wash free from 

 chlorids with hot water. (As a rule, one precipitation of calcium is 



