RECIPES, FORMULAE AND USEFUL HINTS. 143 



Peron's Luting. 



Common resin 

 Red ochre 

 Yellow wax 

 Oil of turpentine 



First melt the wax, then add the resin, next stir in the ochre and 

 lastly the turpentine. According as the ochre or other ingredients pre- 

 ibminate, the luting will be brittle or elastic. Great care should be 

 taken that the mixture does not take fire and the vessel used should be 

 capable of containing at least three times the quantity made at one 

 time. 



Grafting wax. 



Melt together eight oz. resin, three of beeswax and one of lard. Run 

 in sticks. It improves with age. 



Black ink. 



A black ink is frequently desirable and is almost impossible to obtain 

 in the stores. A good ink may be made by boiling eight oz. of pow- 

 dered nut galls and one oz. extract of logwood in three quarts of water 

 for an hour. Strain and add four oz. of copperas (sulphate of iron), 

 three oz. of gum arabic and one of blue vitriol (sulphate of copper) ; 

 let it stand until dissolved and strain again. A few cloves will keep 

 it from moulding. 



Old alcohol which has been discolored by specimens can be cleaned 

 by filtering through animal charcoal, but nothing will completely remove 

 disagreeable odors though a redistillation will sometimes help it. 

 After filtering, the spirit should be brought to a proper strength (to be 

 ascertained by the hydrometer) by adding new alcohol. 



To blacken brass. 



It is occasionally desirable to blacken portions of instruments as stages 

 of microscopes, etc. This may be done by cleaning the brass of all 

 grease, then covering with a solution of nitrate of copper which on the 

 application of heat turns the surface to a jet black. If desirable, it may 

 then be lacquered by applying shellac varnish and heating slightly. ' 



