44G TRANSACTIONS OF THE AMERICAN INSTITUTE. 



These tests were made by the speaker, which proved that the gas iu use 

 was nearly fret, from sulphuretted hydrogen. 



Re-Cutting Files. 



Mr. Watson said some persons were claiming that old files could be 

 renewed by means of sulphuric acid, he would enquire whether any one 

 present had tried the experiment. 



Dr. Rowell said that many years ago he had seen it tried, but there was 

 no value in the process. 



Mr. J. B. Root remarked the process had been tried bj' workmen in the 

 same establishment with him, and it was found that although the file was 

 bright and apparently sharpened, the edge did not remain five minutes 

 after it was put in use. 



The Chairman then presented the following interesting items of scientific 

 news: 



Indestructible Writing. 



M. Lucas proposes for this purpo'^e an ink composed of 20 grains of 

 sugar dissolved in 30 grains of water, to which is added a few drops of 

 concentrated sulphuric acid. By heat the sugar becomes carbonized and 

 when applied to paper cannot be washed off, the stain being made more 

 permanent by the decomposing action of the acid. After the writing is 

 dry the paper should be passed through a weak alkaline solution to remove 

 any excess of acid. 



Manufacture of Aluminum. 



M. Basset, of Paris, has discovered several substitutes for the alkaline 

 metals used to decompose chloride of aluminum, which consist of those 

 metalloids and metals forming by double decomposition chlorides more 

 fusible and volatile than the chlorides of aluminum. Arsenic, borax, 

 cyanogen, zinc, antimony, mercur}', tin and the amalgams of autiinon}^, 

 zinc and tin may be used for this purpose. 



Mr. Watson said this item of news reminded him of the great value of 

 aluminum bronze; a mixture of tin with from eight to ten per cent, of 

 aluminum, as a journal box where rapid rotation Avas required. It would 

 heat but very little. He had seen a wheel revolving *I,100 times a minute 

 which had journals quite cool to the touch. The wheel which he alluded 

 to was in the melodeon establishment of Carhart & Needham. He would 

 recommend this alloy for the journals of fan blowers which are driven at 

 very high velocity. 



Rubidium. 

 Prof Bunsen, in his last account of experiments on this new metal of 

 the alkaline class, states it is more electro-positive than potassium. It 

 exhibits a flame similar to the latter metal when combining with the oxygen 

 of water, but it inflames much quicker in the air. Its specific gravity is 

 about 1.52, At 1-4 deg. P. it is soft as wax; at I0I-3 deg. F. it becomes 

 liquid, and at a red heat is transformed into bluish gray vapor. Its name 

 has reference to the peculiar red line found in its spectrum. 



