252 ANNUAL OF SCIENTIFIC DISCOVERY. 



transparency, present the additional advantage of being useful as a most 

 durable tracing paper. 



In consequence of its strength and resistance to water, vegetable parch- 

 ment would probably find many applications for military purposes; thus it 

 promises to furnish an excellent material for water-proof cartridges. 



Another field of considerable extent for the application of vegetable parch- 

 ment appears to be in book-binding, and especially in ornamental book- 

 binding. The books bound in parchment paper which accompanied your 

 letter, are remarkable for the beauty and solidity of their binding. Expe- 

 rienced book-binders, to whom I submitted these books, believed them to be 

 bound in real parchment. Even in the manufacture of books and maps 

 which, like those used for educational purposes, like military plans and nau- 

 tical charts, have to stand considerable wear and tear, parchment paper may 

 find a very useful application. The printing on ordinary paper is not 

 changed by the treatment Avith sulphuric acid, but owing to the shrinking of 

 the paper during the process, it will, probably, be found more convenient for 

 such purposes to print on the paper after it has undergone the transforma- 

 tion. Vegetable parchment is remarkable for the facility with which printer's 

 ink, as well as writing ink, may be applied to it, and for its attraction for 

 dyes generally, many of which it appears to take even more readily than 

 calico. The specimens of dyed parchment paper which accompanied your 

 letter, leave nothing that could be desired in this respect. 



Among the numerous more or less important applications in which parch- 

 ment paper is sure to be found useful as soon as it becomes accessible to the 

 general public, its adaptation for household, and especially for culinary pur- 

 poses, must not be left unmentioned. 



In closing the orifices of vessels for preserves, etc., few housewives will 

 hesitate to substitute an elegant material like vegetable parchment paper 

 for the animal membrane, so frequently offensive, which is now generally in 

 use. 



Formed into bags, of which the seams are cemented with the white of eggs, 

 parchment paper will be found very useful for the purposes of boiling and 

 stewing, according to the principles of a refined and scientific cuisine. 



Nor can the chemist fail to derive some benefit from so interesting an 

 achievement of his own science as the transformation of paper into parch- 

 ment. 



In the laboratory, vegetable parchment will become a material of general 

 use for connecting retorts and condensers, or other similar apparatus, and on 

 account of its indestructibility by many of the fluids usually employed in 

 electric batteries, it will probably find a further and even more important 

 application in the construction of diaphragms for galvanic apparatus. 



ESTIMATION OF ACETIC ACID IN VINEGAR. 



Mr. Nicholson and Dr. Price have stated that the estimation of acetic acid, 

 by means of carbonate of soda or caustic alkalies, gives results that are not 

 accurate, because the acetate of soda has an alkaline reaction. Prof. Otto 

 has recently made some experiments, with the view of ascertaining whether 

 the error thus caused is constant, or whether it is sufficiently small to be dis- 

 regarded; and has obtained results very different from the above-named 

 chemists. The following numbers represent the percentage of acetic acid in 

 vinegar, as estimated by different methods : 



