Modern magic lanterns; a guide to the ... - Yesterday Image

—BOME-MADB OXYQEN, QAfi HOLDBBS, RTO. 23cork, straw, etc. When the cakes are not employed, twoparts by weight of chlorate to one of manganese are thosewe used in the days when oxygen was not so readily obtainable.Some workers, however, prefer three, or even four partsof chlorate.Whatever retort is used, a gas stove is the most convenientway of heating it ; the heat should be left on untilat least four cubic feet of oxygen have come off per pound ofchlorate. This is mentioned because the emission of gas isoften irregular, ceasing almost and then coming off with fullforce again.When the gas is to be received in a bag, it should bewashed by allowing it to bubble up, as shown in Fig. 17,through a Woolff's bottle containing a fairly strong solutionof caustic soda, which will last for several operations, andthen through an empty flask to remove as much as possibleof the water. This washing is not necessary when apneumatic holder is to be employed. When no more gas iscoming off, the stopcock on the bag should be closed and thetube immediately disconnected between the retort and thefirst bottle ; if this is not done at once and before the retortis allowed in any degree to cool, the liquid in the flask willbe sucked back and an explosionof steam in the retort issure to ensue. There shouldbe no fear of this in any butthe most incompetent hands,which latter had best leavelimelight alone altogether.When a gas bag has got hardthrough cold, it should bewarmed a little before fillingto soften it. If this is not doneHg. w.Apparatus for Makinq tintthe bag will rapidly perish.Washing Oxygen.In filling a bag with oxygenthe sequence of operations should be as follows :(1) Having connected the retort and flasks as shown,and having the empty bag with its stopcock open andtube ready to connect to the last flask, apply heat tothe retort until gas bubbles off freely.