632 The Philippine Journal of Science 192s 



EXPERIMENTAL 



Salts of aluminium, antimony, arsenic, barium, beryllium, 

 bismuth, boron, cadmium, calcium, cesium, cerium, chromium, 

 cobalt, copper, gold, iridium, iron, lead, lithium, magnesium, 

 manganese, mercury, molybdenum, nickel, osmium, palladium, 

 platinum, potassium, rubidium, selenium, silver, sodium, stron- 

 tium, tellurium, thallium, thorium, tin, titanium, tungsten, 

 uranium, vanadium, and zinc were tested with hmt in neutral 

 and acid solution and with hmt plus potassium iodide in neutral 

 and acid solution. 



It was found that solutions of salts of antimony, bismuth, 

 cadmium, gold, iridium, mercury, palladium, platinum, silver, 

 and tin gave characteristic crystalline precipitates with hmt in 

 solutions acidified with hydrochloric acid (silver is used in nitric 

 acid solution). Salts of calcium, ferrous iron, magnesium, man- 

 ganese, and titanium sometimes give crystalline compounds with 

 hmt, but the crystals formed are not especially characteristic. 



When a fragment of potassium iodide is added to a drop of 

 a solution of hmt and a salt of antimony, bismuth, cadmium, 

 palladium, platinum, or tin, characteristic crystalline compounds 

 result. Calcium, iron, magnesium, and manganese 4 salts yield 

 crystals which cannot be easily differentiated one from another. 

 Free hydrochloric, sulphuric or nitric acid gives crystals with 

 hmt and potassium iodide, but these crystals are easily distin- 

 guished from those formed with anv of the above-mentioned 

 metals (Plate 2, fig. 12). 



Technic— Of the various general methods of making micro- 

 chemical tests, 5 the most satisfactory procedure proved to be 

 that in which a fragment of the solid reagent is added to a drop 

 of the solution of the substance to be tested. This drop should 

 be from 2 to 4 millimeters in diameter. The preparation on 

 the slide is then examined under a low-power microscope. Dilute 

 solutions yield more nearly perfect crystals than concentrated 

 ones. Scratching the drop with a small glass rod or platinum 

 spatula is sometimes advantageous. 



4 Other metallic salts, such as those of arsenic, cobalt, lead, nickel, osmium, 

 strontium, tellurium, and zinc yield crystalline compounds with hmt and 

 with hmt and potassium iodide, but these compounds, being very soluble, 



"Charnot, E. M., Elementary Chemical Microscopy, 1st ed. (1916) 

 261-259. 



