CHEMICAL SCIENCE. 235 



been made with metallic iron or with whijh metallic iron had been immersed, 

 and directed attention to the fact that though the depth and body of color 

 seemed to be deepened, yet in every case the durability of writings made with 

 such inks was so impaired that they became brown and faded in a few months. 

 The most permanent ordinary inks were shown to be composed of the best 

 blue gall nuts with copperas and gum, and the proportions found on experi- 

 ment to yield the most persistent black were six parts of best blue galls to 

 four parts of copperas. Writings made with such an ink stood exposure to 

 sun and air for twelve months without exhibiting any change of color ; while 

 those made with inks of every other proportion or composition, had more or 

 less of their color discharged when similarly tested. This ink, therefore, if 

 kept from molding and from depositing its tannogallate of iron, would afford 

 writings perfectly durable. It was shown that no gall and logwood ink was 

 equal to the pure gall ink in so far as durability in the writings was concerned. 

 All such inks lost their color and faded sooner than pure gall inks, and several 

 inks were exhibited which, though durable before the addition of logwood, 

 faded rapidly after logwood was added to them. Sugar was shown to have 

 an especially hurtful action on the durability of inks containing logwood in- 

 deed, on all inks. Many other plain inks were exhibited, and their properties 

 described as gallo-sumach ink, rnyrobalans ink, Kange's ink inks in which 

 the tannogallate of iron was kept in solution by nitric, muriatic, sulphuric, and 

 other acids, or by oxalate of potash, chloride of lime, etc. The myrobalans 

 was recommended as an ink of some promise for durability, and as the cheap- 

 est ink it was possible to manufacture. All ordinary inks, however, were 

 shown to have certain drawbacks, and the author endeavored to ascertain by 

 experiment whether other dark substances could be added to inks to impart 

 greater durability to writings made with them, and at the same tune prevent 

 those chemical changes which were the cause of ordinary inks fading. After 

 experimenting with various substances, and among others, with Prussian blue 

 and indigo dissolved in various ways, he found the sulphate of indigo to fulfil 

 all the required conditions and, when added in the proper proportion to a 

 tannogallate ink, it yielded an ink which is agreeable to write with, which 

 flows freely from the pen, and does not clog it ; which never molds, which, 

 when it dries on the paper, becomes of an intense pure black, and which does 

 not fade or change its color, however long kept. The author pointed out the 

 proper proportions for securing these properties, and showed that the smallest 

 quantity of the sulphate of indigo which could be used for this purpose was 

 eight ounces for every gallon of ink. The author stated that the ink he pre- 

 ferred for his own use was composed of twelve ounces of gall, eight ounces of 

 sulphate of indigo, eight ounces of copperas, a few cloves, and four or six 

 ounces of gum arable, for a gallon of ink. It was shown that immersing iron 

 wire or filings in these inks destroyed their durability, as much as similar 

 treatment destroyed ordinary inks. He therefore recommended that all legal 

 deeds or documents should be written with quill pens, as the contact of steel 

 invariably destroys more or less the durability of every ink. The author con- 

 cluded his paper with a few remarks on copying inks and indelible inks, show- 

 ing that a good copying ink has yet to be sought for, and that indelible inks, 



