550 



SCIENCE 



[N. S. Vol. XXX. No. 773 



chemist wishes to be rid are heavier than 

 air. Besides the fan draft in the hood the 

 flue should be so arranged that a good 

 sized Bunsen burner can be kept burning 

 in it for use when the fans are not running. 



Hoods.— These can in general be disposed 

 of about the laboratory walls and be con- 

 structed of wood, pine, white wood, cypress 

 or "asbestos wood" or " asbestolith " with 

 wooden or asbestolith sashes. Where the 

 material is exposed to steam, hot air, or un- 

 usually corrosive agents, they perhaps can 

 be made of glass, wired glass, admitting of 

 large panes set in lead-covered sashes. 



Iron settings for the glass, unless kept 

 well painted, are not to be recommended. 

 Possibly these sashes may be omitted, and 

 the hoods built after the manner of show 

 eases of plate-glass show windows, by drill- 

 ing and holding the glass plates in position 

 by angle irons kept well painted with a 

 pitchy "paint." The backs and tops of 

 the hoods can be lined with the same ma- 

 terial, where wood is inadmissible, and it is 

 desired to secure freedom from scaling 

 from the brick walls. The use of hoods ex- 

 tending over each desk, as in Edinburgh, 

 is of doubtful expediency and renders the 

 laboratory dark and fills the ceiling up 

 with their exit pipes. The use of small low 

 hoods at each desk would seem to render 

 the piping system complicated and expen- 

 sive. Except in very special cases the ne- 

 cessity of an individual hood close at hand 

 is not very great. The bottoms can be made 

 of concrete or wire lath, tile or soapstone, 

 and the hoods should not be more than 18 

 inches deep. The duets from the hoods can 

 be made square or rectangular, of the wood 

 or the asbestos compositions mentioned. 

 If of wood they can be grooved and 

 tongued, glued and nailed together and 

 varnished. If made of iron they should be 

 painted with an asphalt or pitchy paint, as 

 "chrysolite" (Solvay Process Co.). Alu- 



minum paint is not found to protect iron 

 as well as has been claimed for it. 



Laboratory Desks and Lockers.— So far 

 as the writer's experience goes, the respon- 

 sibility for their selection lies usually with 

 the architect, and it is common experience 

 that architecture and chemistry do not 

 "mix"; that is, good architectural stu- 

 dents are oftentimes deficient in chem- 

 istry. 



Quartered-oak desks and alberene stone 

 tops seem almost as much out of place amid 

 the fumes and acids of a chemical labora- 

 tory as dress suits for the students. Even 

 a casual visitor can not help having a pang 

 of regret to see a fine quartered oak panel 

 ruined by the attack of sulphuric acid or 

 caustic soda. Speaking from wide observa- 

 tion and the experience of others, the 

 writer is convinced there is no better (and 

 in the long run cheaper) material for the 

 tops of ordinary laboratory desks than 

 wood. Tiling is always uneven, lead is un- 

 tidy and expands but does not contract 

 when heated, glass cracks, and all are cold 

 to the touch. For the tops of laboratory 

 desks or tables the following woods have 

 been found to give good satisfaction: 

 Northern pine, whitewood, cedar and Cali- 

 fornia redwood. These may be finished with 

 equal parts of linseed oil and turpentine, or, 

 better, filled with aniline black made in the 

 pores of the wood, according to the follow- 

 ing procedure : Apply to the wood solution 

 one, and after it has dried in, solution two : 

 Solution I., 100 grams aniline hydrochlo- 

 ride, 40 grams salammoniac, dissolved in 

 650 e.c. of water. Solution II., 100 grams 

 copper sulphate, 50 grams potassium 

 chlorate, dissolved in 650 c.c. of water. 

 Oak, ash, or cypress can not be recom- 

 mended, the former two because they 

 shrink too much and the last because it 

 is very splintery. If the tops are made of 

 two-inch stuff they can be planed down 



