444 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



were made in regard to the different degrees with which va- 

 rious colors were taken up alter the same preparation ; and, 

 as a general result, it was ascertained that there was a great 

 inferiority in this respect in the silk of the new worm, al- 

 though it is possible that some treatment may be devised 

 which will render the difference less palpable. G (7, April 28, 

 1870,156. 



STAINING MARBLE YELLOW. 



Inquiry was recently made by a technical society in Prus- 

 sia for a treatment of white marble that would impart to it 

 a permanent uniform yellow color, equal to that of antique 

 marble, and one that could be made dark or light at will, 

 penetrating at least one twelfth of an inch into the stone, but 

 not affecting its chemical character. Of the several solutions 

 offered, that of Professor Weber seems to have been most sat- 

 isfactory, and is based upon the fact, hitherto not brought to 

 practical application, that solutions of iron salts in strong 

 alcohol are not decomposed by carbonate of lime, while, on 

 the other hand, the aqueous solutions of the same salts are 

 readily decomposed by the lime. Another important consid- 

 eration is the fact that alcohol is more easily taken up by 

 marble than water, and that the tendency to absorption may 

 be increased very greatly by heating the marble to a certain 

 temperature. If, then, the alcoholic solution referred to be 

 applied to the dried marble, and this subsequently moistened 

 with water, the oxide of iron that has penetrated the material 

 of the stone is decomposed by the carbonate of lime, and is 

 separated in the form of a finely divided oxide, not separable 

 from the particles of marble. 



In the practical application of the principles just enumer- 

 ated, a neutral chloride of iron is to be first dissolved in nine- 

 ty per cent, of alcohol, and after gently heating the marble to 

 be colored in an oven or over a fire, the solution in question 

 is to be applied by means of a brush, a sprinkler, or by some 

 other similar apparatus, or even by pouring the solution over 

 it. It will, of course, be understood that the strength of the 

 solution is to be proportioned to the depth of the color de- 

 sired ; and care must be taken, also, in regard to the degree 

 of temperature. For the production of light tints it is con- 

 sidered preferable to apply very diluted solutions repeatedly. 



