1825.] • Seleniurets of the Eastern Harz. 285 



tity of selenium. On the contrary, by precipitating the selenium 

 from the acid solution by sulphurous acid, we do not obtain the 

 whole of it, because a small quantity of seleniate of lead, and 

 even of sulphate and chloride of lead, are thrown down at the 

 same time. 



The apparatus I employed in these analyses is nearly the same 

 as that which M. Berzehus used in his analysis of grey nickel. 

 I welded two tubes to a small glass bulb ; one of the tubes was 

 of small diameter, and four inches long ; the diameter of the 

 other was much larger, and its length twelve inches. Having 

 bent the latter to a right angle, near the middle, I weighed the 

 whole apparatus, then introduced the pulverised mineral, and 

 weighed it again. The smaller tube was joined to an apparatus 

 in which chlorine was very slowly disengaged, and the gas was 

 dried by chloride of calcium. The bent tube passed into a 

 bottle, filled two-thirds with water, traversing a perforated cork, 

 which did not close the bottle hermetically, and dipping only a 

 few lines deep into the water. 



The apparatus being filled with chlorine, the bulb was very 

 gently heated by a spirit-lamp. Chloride of selenium formed 

 and sublimed. Protochloride of selenium forms at first, and 

 flows through the tube, as an orange coloured liquid, into the 

 water in the bottle, where it deposits selenium, the greater part 

 of which is afterwards redissolved by the chlorine which traverses 

 the liquid. Afterwards scarcely any thing but perchloride of 

 selenium is formed, which has great resemblance to the perchlo- 

 ride of phosphorus; it condenses in the tube, and would choak 

 it up if its diameter were not pretty considerable. It is neces- 

 sary very frequently to volatihse the chloride which condenses in 

 the tube near the bulb, by the flame of a small lamp, and thus 

 make it pass over into the water in the bottle, which, if the 

 quantity be large, is somewhat difficult. The chlorine must be 

 very slowly liberated ; for if the bubbles of gas rise too rapidly 

 through the water, the chloride of selenium which they contain 

 has not time to be decomposed by the water, and a portion 

 escapes by the little aperture in the cork undecomposed. 



1 caused chlorine to pass over the mineral for half a day ; all 

 the metals were then perfectly changed into chlorides. The 

 operation was at an etid when chloride of selenium ceased to be 

 formed. The bulb was then cautiously cooled lest the glass 

 should crack by the cooling of the fused chloride of lead. 

 When cold I cut off" the part of the wide tube which still con- 

 tained chloride of selenium, and dropped it into the liquid in the 

 bottle. After having washed it, I weighed the tube with the 

 bulb containing the fixed chlorides. If the mineral contained 

 iron, a portion of the chloride of iron was found in the tube, and 

 the remainder with the fixed chlorides. 



