CHEMICAL LABORATORY AT THE UNIVERSITY OF SYDNEY. 181 



To prevent leakage of fumes into the rooms from the window 

 draught cupboards the sash is pr'ovided with felt cushions. India- 

 rubber was tried by Dr. Armstrong at South Kensington, but 

 found to be unsuitable for this purpose, as there was too much 

 friction, and moreover the indiarubber became hard and decayed. 

 All the wood work is thickly varnished, to prevent its being 

 destroyed by acid fumes. 



For the benches in the practical class room it is proposed to 

 have six-inch flues proceeding downwai'ds, with small moveable 

 hoods or cowls with trumpet-shaped mouths, and arranged 

 in such a way that evaporations can be carried on under 

 them without much fume finding its way into the room. The 

 cowls do not rise high enough to materially obstruct the view ; 

 they and the pipes leading from them will be made either 

 of earthenware or of sheet-iron lined with asbestos board. 

 The form (Plate IX.) is so arranged that the student will be able 

 to see into the evaporating basin, even when it is under the hood. 



Artificial draught by furnaces has been relinquished in 

 England and on the Continents of Europe and America ventilating 

 furnaces do well enough, since artiflcial warming is necessary for 

 naost of the year, but in Sydney this is not required. 



Small openings are provided in the draught closets for admitting 

 fresh air, so that it is not always necessary to raise the sash for 

 that purpose. 



It does not do to have the draught cupboards too large, 

 otherwise the air is not changed quickly enough, and the fumes 

 hang about inside. To facilitate their removal the upper part is 

 made to slope inwards on all sides in the draught closets on the 

 benches, and from the back in the window draught cupboards. 

 The roof of the closets always presents more or less difliculty — 

 Avood is liable to warp, char, or catch fire, plaster falls down and 

 slate cracks, iron rusts and scales off — but if not too low glass 

 answers well enough. 



At Strasboui'g coarse ii'on-wire gauze, coated with cement, 

 fixed in iron frames, is used. At the Finsbury Technical College 

 galvanized iron thickly varnislied is employed, but here I intend 

 to try asbestos board. 



The draught exit is made with a flattened trumpet mouth 

 at a height of about twelve inches from the floor of the 

 bench draught cupboards, so that an evaporating basin may be 

 placed dii'ectly opposite to it. The minor openings into the 

 draught-closets are made in front as usual, to keep the fumes 

 away from the operator as much as possible. 



SULPHURETTED HYDROGEN. 



A gas-holder for the supply of this gas is placed outside. It is 

 to be five feet in diameter by seven feet high, made of lead or 

 stout sheet-iron, coated with well baked, bitumen. The taps are 



