L. TECHNOLOGY. 461 



with dilute sulphuric acid (one part to three of water). A 

 thin layer of sulphate of lime is thus formed upon the wall, 

 which is not attacked by the vinegar fumes at least, and con- 

 sequently remains firm. Ordinary plastering, as is well 

 known, contains carbonate of lime, which is gradually trans- 

 formed into acetate of lime by the vapor of the vinegar, and 

 as such scales off from time to time. 5 (7, xxvi., 208. 



WATER-PROOF GLUE. 



A glue, which is said not to be affected by moisture, may 

 be prepared by dissolving one ounce of sandarac and one 

 ounce of mastic in half a pint of alcohol, and adding one 

 ounce of white turpentine. A very thick glue is then to be 

 made, to which some isinglass is to be added. The alcoholic 

 solution is to be heated in a vessel to boiling, and poured 

 gradually, with constant stirring, into the warmed glue, until 

 the whole is intimately mixed together. The mixture is final- 

 ly to be strained through a cloth, and is then ready for use, 

 and is to be applied hot. It dries quickly, becomes very hard, 

 and pieces of wood united with it do not separate in water. 

 15 (7, 1870,111. 



PREVENTING MOULD IN MUCILAGE. 



Solutions of gum arabic are very liable to become mouldy, 

 and, while the introduction of creosote, corrosive sublimate, 

 etc., frequently used to remedy this evil, is objectionable on 

 account of the danger of poisoning, according to the Industrie 

 Blatter sulphate of quinine is a complete protection against 

 mould, a very small quantity of it being sufficient to prevent 

 gum mucilage from spoiling. It is quite possible that writ- 

 ing-ink might be protected by the same application from a 

 like difficulty. The use of ammonia for the same purpose is 

 also recommended. 8 (7, 1871, xvl, 127. 



FASTENING PARCHMENT PAPERS. 



The use of parchment paper has hitherto been extremely 

 limited, for the want of a glue that would resist equally well 

 both dry and moist heat. It is now stated that the Brothers 

 Jacobsen, of Berlin, have succeeded in overcoming this diffi- 

 culty by preparing a paste which has been found, on being 

 subjected to a most severe test on an extensive scale, to meet 



