CHEMICAL SCIENCE. 221 



Writing traced with a quill or gold pen dipped in this ink dries to a pale 

 blue color; but if now a heated iron be passed over its surface, or the page 

 of manuscript be held near a tire, the Avriting will quickly assume a jet black 

 appearance, resulting from the carbonization of the sugar by the warm acid, 

 and will have become so firmly engrafted into the substance of the paper as 

 to oppose considerable difficulty to its removal or erasure by the knife. On 

 account of the depth to which the written characters usually penetrate, the 

 sheets of paper selected for use should be of the thickest make, and good 

 white cartridge paper, or that known as " cream laid," preferred to such as 

 are colored blue with ultramarine; for, in the latter case, a bleached halo is 

 frequently perceptible around the outline of the letters, indicating the partial 

 destruction of the coloring matter by the lateral action of the acid. 



The writing produced in this manner seems indelible; it resists the action 

 of "salts of lemon," and of oxalic, tartaric, and diluted hydro-chloric acids, 

 agents which render nearly illegible the traces of ordinary black writing ink; 

 neither do alkaline solutions exert any appreciable action on the carbon ink. 

 This material possesses, therefore, many advantageous qualities which would 

 recommend its adoption in cases where the question of permanence is of 

 paramount importance. But it must, on the other hand, be allowed that such 

 an ink, in its present form, would but inefficiently fulfil many of the require- 

 ments necessary to bring it into common use. The peculiar method of 

 development rendering the application of heat imperative, and that of a 

 temperature somewhat above the boiling point, of water, together with the 

 circumstance that it will be found impossible with a thin sheet of paper to 

 write on both sides, must certainly be counted among its more prominent 

 disadvantages. 



ACTION OF PROLONGED HEAT AND WATER ON DIFFERENT 



SUBSTANCES. 



Mr. H. C. Sorby communicates to the French Academy an account of some 

 experiments he has made on the above subject. He put different substances 

 and various solutions in glass tubes, sealed them hermetically, and then 

 placed them in the boiler of a high-pressure engine, and kept them there, 

 exposed to a temperature ranging from one hundred and forty-five to one 

 hundred and fifty degrees Centigrade, for some months. Others he placed in 

 an ordinary kitchen boiler, in which the temperature varied from seventy- 

 live to one hundred degrees Centigrade. The first facts noticed are the 

 decomposition of the glass tubes employed. Crown glass resisted the action 

 best, better even than Bohemian, but it was sometimes acted on at but 

 slightly elevated temperatures. English flint glass was easily decomposed 

 by the prolonged action of water below one hundred degrees. A fragment 

 of flint or Bohemian glass, enclosed in a tube of crown glass with a little 

 water, was more quickly decomposed than with much water. A moderately 

 strong solution of nitric acid had little or no action on flint glass at one 

 hundred and forty-five or one hundred and fifty degrees, while pure water 

 soon changed it into a white crystalline mass. Wood, exposed to a tempera- 

 ture of one hundred and forty-five degrees, without water, underwent but 

 little change, while some with water became quite black. A brilliant black 

 substance separated from the wood, but the water remained quire clear, 

 although it had an acid reaction, due, no doubt, to acetic acid, and when the 



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