470 Scientific Intelligence. 



accord to absolute zero, no matter whether the surrounding objects 

 be at absolute zero or not. The authors give a name, heat-point, 

 to the temperature at which a substance will begin to vibrate its 

 molecules under the influence of heat. 



It should be added that the authors assume that rotary molecu- 

 lar motion would be stopped by pressure, and that they disre- 

 gard intra-molecular vibration. Their deductions are based upon 

 an entirely unproven assumption ; but if it is a true one its 

 bearing upon the condition of matter in the interior of the earth, 

 for instance, is interesting. — Ghem. JVeios, lxxxv, 194. h. l. w. 



2. New Method for Assaying Pyrites. — To determine gold and 

 silver in ores consisting chiefly of iron pyrites, Buddetjs j3laces 

 100 or 200 8 ', according to its richness, of the finely pulverized 

 substance in a covered, smooth clay crucible and heats to redness 

 in a muffle for one-half to three-quarters of an hour, until all 

 trace of the sulphur flame has disappeared. The mass, which is 

 loosely aggregated, is transferred to a dish or beaker of about 

 1000 cc capacity, any dust being removed by means of a camels- 

 hair brush. It is then treated with 250 or 500 cc of a mixture of 

 equal volumes of strong hydrochloric acid (free from arsenic) 

 and water, and, after standing for about an hour in a warm place, 

 the same quantity of the acid mixture is added, and the whole is 

 boiled for some time. Ferrous sulphide, which forms the greater 

 part of the ignited substance, is thus dissolved, leaving the gold 

 and silver in the residue. When the sulphide is completely 

 decomposed the liquid is diluted with water until the vessel is 

 nearly full, and filtered. The residue is washed two or three 

 times with water, then dried, transferred with the filter-paper to 

 a Hessian crucible of 150 or 300 cc capacity, mixed by means of a 

 spatula with 50 or 100 s of assay lead and 5 or 10 s of borax, and 

 finally fused in a muffle. It is of advantage to use 100 or 200 g " 

 of a mixture of equal parts of acetate of lead and caustic soda 

 instead of assay lead. After cooling, the crucible is broken, and 

 the lead is cuppelled. Gold and silver are then parted as usual. 

 The method appears to be more accurate and less expensive than 

 those usually employed. — Ghem. Zeitung, xxiv, 922. h. l. w. 



3. Germanium Hydride. — Voegelen has discovered the fact 

 that when hydrogen is evolved by means of sodium amalgam or 

 zinc and sulphuric acid from solutions containing germanium, the 

 gas contains a small quantity of germanium hydride. The hydro- 

 gen burns with a bluish-red flame which deposits a bright mirror 

 upon porcelain. Mirrors are formed also when the gases are led 

 through hot glass tubes, as in the Marsh test for arsenic. These 

 have a tin-white color, and show a red color in transmitted light 

 and a green color in reflected light. When the gases are passed 

 through silver nitrate solution, a compound of germanium and 

 silver is precipitated. Attemj)ts to condense the germanium 

 hydride by cooling the hydrogen with solid carbon dioxide and 

 ether were without success, hence the hydride was not obtained 

 in a pure condition. From the analysis of the precipitate pro- 



