128 Mr. Macabam on the Paper Manufacture. 



specific gravities than formerly, the rags being even then more thoroughly 

 cleansed. In one of the paper works, the use of the caustic ley had thus 

 efiected a saving of 80 lbs. of soda-ash per day, or one-fourth of the 

 material previously in use. As different strengths of leys are employed for 

 the cleansing of the different kinds of rags, it was found that the possessing 

 of a standard ley was advantageous. By this means a scale of measures 

 had been adopted for charging the boilers for each variety. As the 

 obtaining of a standard ley of a uniform strength, necessitated a constancy 

 in the per centage of alkali in the soda-ash, the usual alkalimetry process 

 was introduced, for the purpose of testing the ash on its an'ival at the 

 works. Mr. Macadam, before leaving this part of the subject, referred 

 to two errors, not uncommon among manufactm-ers requiring caustic soda. 

 First, The use of an aqueous solution of lime alone, obviously unaware of 

 the slight solubility of that substance in water, and its decarbonating 

 function ; and Secondly, The using of the materials in the cold state, a 

 practice very general amongst soap boilers, and indeed in some cases pre- 

 ferred by them. Although the digestion, under such circumstances, be a 

 lengthened one, the maximum of causticity of the carbonated alkali is not 

 obtained. 



The solvent action of caustic leys on glass instruments was also 

 adverted to. Chemists have long known that water exercises a very 

 decided solvent action upon glass, especially when containing traces of 

 Fluorine compounds, as has been lately shown by Dr. George Wilson, in 

 reference to the corrosive action of some of the Edinburgh waters on glass 

 instruments in use by brewers. As might be expected, alkaline solutions 

 act much more powerfully, especially at liigh temperatures. From some 

 observations made by Mr. llobert Clarke of the Campsie alum works and the 

 author, glass hydrometers have been found to give way from this solvent 

 action after a few months usage in hot and concentrated alkaline solutions; 

 while others gave erroneous indications, to the extent of three or four 

 degrees, because of the lightening of the instruments by the material 

 removed fi-om their surfaces. Mr. Clarke has instituted experiments to 

 determine the rate of this solvent action, by weighing carefully a number 

 of instruments before and after various periods of usage. Cold alkaline 

 solutions act more slowly, but the action is still a marked one, and points 

 to the necessity of devising some means of removing this source of error, 

 in the determination of the strengths of leys. The coating of the instru- 

 ment with gutta percha dissolved in chloroform might serve the purpose 

 in regard to cold liquors, since the envelope adds little to its weight, and 

 is transparent and unacted on by alkalies ; but such an application is 

 obviously useless in determining the specific gravity of solutions of 

 elevated temperatures. 



In reference to the bleaching process — bleaching powder, being variable 

 in quality, being liable to adulteration and other causes of inferiority, a 

 testing process is just as essential for a knowledge of its value, as in the 

 case of alkaline compounds, for the determination of the pure alkali present 



