182 Miscellaneous Intelligence, 



according to M. Van Mons, is an oxidated sulphuret of silicinin. — 

 Bull. Univ. A. xl. 478. 



18. On the Production of Artificial Ultramarine. — The possibility 

 of making ultramarine was first observed, when the blue matter 

 found in a soda furnace was shewn by Vauquelin to have the 

 properties of that pigment ; and since then the experiments of 

 Gmelin and Guimet have proved highly satisfactory and successful ; 

 but as the processes published are still expensive, M. Kuhlman has 

 been induced to publish an observation he has made, in hopes it 

 may assist in simplifying them. Whilst repairing a reverberating 

 furnace for the calcination of sulphate of soda, he remarked that the 

 brick bridge, separating the salt from the fire, was covered in dif- 

 ferent places with a coat of ultramarine. It appeared that, previous 

 to the formation of the ultramarine, a sulphuret of sodium was pro- 

 duced, for the blue places were surrounded by small, brilliant, 

 reddish-brown crystals of this sulphuret. 



Whether the sulphate of soda is decomposed by the action of 

 heat only, or by the simultaneous action of the heat and the fuel, 

 or by the influence of the silica and alumina of the clay in the 

 bricks, are questions M. Kuhlman could not answer ; but the im- 

 portant point of being able to make artificial ultramarine, by the 

 action of clay and sulphate of soda, was distinctly ascertained. It 

 is also remarked, that sulphate of soda, prepared without any excess 

 of acid, may be converted into sulphuret, and become reddish- 

 brown by the sole influence of heat ; but that when excess of acid is 

 present, this decomposition cannot take place, and no ultramarine 

 can be formed. — Annates de Chimie, xl. 439. 



19. Adulteration of Chromate of Potash ; its detection. — The 

 chromate of potash has the power of combining with other sails of 

 potash up to a certain extent, without any very sensible change in 

 its form and appearance ; and hence it has been sent into the 

 market for the dyers, falsified by considerable quantities of sulphate 

 and muriate of potash, the presence of which it has been difficult to 

 ascertain. M. Zuber has, in consequence, and in consideration of 

 the power of vegetable acids upon it, devised the following process 

 for this purpose : — Add a large excess of tartaric acid to the chro- 

 mate of potash to be tried, the chromate will be decomposed, and 

 acquire, in about ten minutes, a deep amethyst colour. It will now, 

 if pure, form no precipitate with the nitrates of baryta or silver, by 

 which means the presence of muriate or sulphate of potash may be 

 readily ascertained. — Bull, de Mulhause. 



20. Sympathetic Ink. — A weak solution of nitrate of mercury 

 forms a good sympathetic ink on paper. The characters become 

 black by heat. 



