1018 CYANITE 



ment to enable the pot to be arrested at any desired height. The pot being heated to 

 redness, the mixture is to be thrown in by small portions until the vessel is half full ; 

 the heat buiug allowed to rise gradually until the whole flows pretty quietly. During 

 the fusion the contents are to be stirred with a clean iron rod to promote the aggre- 

 gation of the spongy sediment. As soon as the rod, on being dipped into the 

 mass and removed, brings with it a pure white porcelain-like product, the operation 

 may be regarded as terminated, and the pot is to be raised from the fire by means of 

 the crane and sling in a slightly inclined position. One of the operators now holds a 

 large clean iron ladle under the edge of the pot, while another elevates the latter wit h 

 the aid of tongs, so that the ladle becomes filled. The contents of the first ladlo aro 

 then poured off into another held by the assistant who tilted the pot. The latter then 

 pours the contents of his ladle into a large, shallow, and brilliantly clean brass Imsiu 

 standing in another containing a little water so as to cool the fused cyanide rapidly. 

 Kxtreme care must be taken to prevent even the smallest drop of water from finding 

 its way into the brass vessel, becaiise on the hot cyanide coming in contact with it an 

 explosion would occur, scattering it in every direction to the great danger of the 

 persons in the vicinity. The two ladles are to be kept very hot, by being held over 

 the fire until wanted, in order to prevent the cyanide from chilling until it is pouretf 

 into the brass basin. The latter should be about 18 inches in diameter and l| deep. 

 It should be quite flat-bottomed. The object of so many pourings off is to prevent any 

 of the sediment from finding its way into the product, and thus causing black specks 

 in it. The pot, on being emptied as far as convenient, is to have the sediment 

 removed and a fresh charge inserted. As soon as the coke of cyanide is cool, it is to 

 be broken up into moderate-sized pieces and placed in dry and well closed jars. 



The cyanide of potassium possesses great points of interest for the technical and 

 theoretical chemist. It is the salt from which an immense number of compounds of 

 importance may be obtained. Very large quantities are made for the purpose of 

 preparing the auro- and argento- cyanides of potassium for the electro-platers and 

 gilders. 



Auro-cyanide of potassium is capable of being formed in several ways. The follow- 

 ing are convenient processes. The selection of a mode of preparing it will depend 

 upon the circumstances under which the operation is situated. 1. By the battery. 

 This process is perhaps the most generally convenient and economical for the 

 electro-gilder. A bath is prepared by dissolving the best commercial cyanide of 

 potassium in good filtered or distilled water. The best salt is that sold under the 

 name of ' gold cyanide.' A Daniell's battery of moderate size being charged, two 

 plates of gold are attached to wires and connected with it. The larger, which is to 

 be dissolved, is attached to the positive, and the smaller, which need be but the size 

 of a flattened wire, to the negative pole. The action of the battery is kept up until 

 the desired amount is dissolved. It is easy to remove the plate used, dry and weigh 

 it at intervals so as to know the proper time to stop the operation. 2. Teroxide 

 of gold (prepared with magnesia) is to be dissolved in a solution of cyanide of 

 potassium. 



Argento-cyanide of potassium. This solution is easily prepared for the electro- 

 plater by the following process. Metallic silver is dissolved in nitric acid and 

 the solution evaporated to dryness. The residue is dissolved in distilled water 

 and filtered. To the solution cyanide of potassium, dissolved in distilled water, is 

 added as long as precipitation takes place, but no longer, The precipitate is filtered 

 off on calico strainers, and well washed with distilled water. It is then to be dissolved 

 in solution of cyanide of potassium and diluted to the desired strength. The solution 

 is frequently dark coloured at first, but it becomes colourless in a few hours, and 

 should then be filtered from a small black precipitate which will be obtained. Many 

 operators neglect the filtration and washing of the precipitated cyanide of silver, and 

 merely continue the addition of the solution of cyanide of potassium to the nitrate of 

 silver until the precipitate at first formed is re-dissolved. The first method is 

 however to be preferred. Some, instead of precipitating with cyanide of potassium. 

 do so with solution of common salt, and then, after washing off the precipitated 

 chloride of silver, dissolve it in cyanide of potassium. Argento-cyanide of potassium 

 can also be prepared with the battery by the process mentioned under auro-cyanide of 

 potassium ; this method is so convenient where the proper apparatus is at hand, that 

 few professional electro-platers would use any other method. 



CYANIDES FERRO. See FKRROCTANIDES. 



CYANIDE OP POTASSIUM:. See CYANIDES. 



CYAKTINE. A name given to Chinoline Blue. See CRINOLINE BLUE. 



CYAKTTE. Kyanite or Disthenc. A native silicate of alumina, occurring 

 generally in flattened prisms of a blue colour. Transparent, finely-coloured speci- 

 mens have occasionally been cut and polished as gem-stones, and bear some resem- 



