258 report — 1859. 



the results ; for an increased quantity of mineral matter makes the thorough com- 

 bustion of the evaporated mass more difficult, and so necessitates the application of 

 a very high temperature, which produces error, by volatilizing a portion of the 

 mineral matter. 



This is not an exact method of estimating combustible or organic matter, there 

 being none ; still it is as correct as any known, and affords uniform results, which 

 the ordinary process assuredly does not. 



Mr. C. J. Burnett exhibited some specimens illustrating the use of Platinum in 

 Photography. 



On the Ageing of Mordants in Calico Printing. 

 By Walter Crum, F.R.S. 



The process of " ageing " in calico printing is that by which a mordant after being 

 applied to a cotton fabric, is placed in circumstances favourable to its being incor- 

 porated with and fixed in the fibre ; and the method usually employed has been to 

 suspend mordanted goods in an apartment in single folds, exposed to the atmosphere. 



The object is to moisten the acetates of iron and of alumina in order to their de- 

 composition; and in ordinary circumstances a pound of water is gradually absorbed 

 by fifteen pounds of printed cloth. The protoacetate of iron is thus enabled, by 

 imbibing oxygen, to become a sesquiacetate like the bisalt of alumina. Each then 

 proceeds to give off acetic acid, and to deposit a tersesquihydrate upon the fibre. 



Various methods have been employed in this country for adding to the natura. 

 moisture of the air, but with no great advantage, until Mr. Jones introduced into 

 Messrs Schwabe's works near Manchester a system of ageing which he had seen in 

 operation at Mulhausen, and succeeded, by the direct iatroduction of steam under- 

 neath, greatly to increase the heat and moisture of the large apartment in which 

 his mordanted goods were hung, and thus to render the process of ageing not only 

 more speedy, but much more perfect than before. But the employment of steam 

 was in that case limited in amount, chiefly by the discomfort to which it subjected 

 the work people in the apartment, and by the damage produced by drops of water 

 falling from their persons upon the goods. 



In the summer of 1856, Mr. Jones visited Thornliebank, and described that me- 

 thod of ageing. It became then not difficult to conceive that, by a further increase 

 of heat and moisture in an apartment sufficiently capacious, and by employing a 

 great number of rollers, goods might become sufficiently moistened without manual 

 labour by being merely passed through such an atmosphere ; and that thus, the 

 pieces being stitched end to end, a continuous process might be substituted for that 

 of hanging goods over wooden rails, and leaving them there until the ageing is 

 completed. 



The idea of passing printed goods through an atmosphere artificially moistened 

 was not new. It had even been patented by Mr. John Thom of Manchester ; but 

 the apparatus of that gentleman was too small to be practically useful. The present 

 improvement consists in rendering the process a practicable one ; and the various 

 adaptations introduced for that purpose will appear in its description. 



A building is employed 48 feet long inside and 40 feet high, with a midwall from 

 oottom to top running lengthwise, so as to form two divisions each 11 feet wide. 



In one of these divisions the goods first receive the moisture they require. Besides 

 the ground floor, it has two open sparred floors 26 feet apart, upon each of which is 

 fixed a row of tin rollers, all long enough to contain two pieces of cloth at their breadth. 

 The rollers, being threaded, are set in motion by a small steam-engine, and the goods 

 to be aged, which are at first placed in the ground floor, are drawn into the chamber 

 above, where they are made to pass over and under each roller, issuing at last at the 

 opposite end and folded into bundles on one (at a time) of three stages which are 

 placed there. These stages are partially separated from the rest of the chamber by 

 a woollen partition. 



While the goods are traversing these rollers, they are exposed to heat and moisture, 

 furnished to them by steam, which is made to issue gently from three rows of trum- 

 pet-mouthed openings. The temperature is raised to from 80 to 100° or more of. 



