Patented Nov. 5, 1929 1,734,562

UNITED STATES PATENT OFFICE KENNETH. F. COOPER, OF GREAT NECK, NEW YORK SODIUM CYANIDE COMPOUND AND PROCESS OF PRODUCING THE SAME, No Drawing. Application filed November 1, 1922. Serial No. 598,430. This invention relates to the production terial which can be used in those industries of Sodium cyanide, which has a relatively high at present requiring high test, or compara degree of purity, and has for its object to tively pure cyanide compounds. improve the products and the processes here My invention consists in the following tofore known. steps: I dissolve the crude patented cyanide 55 With these and other objects in view, the in water and treat the solution with a sodium invention consists in the novel steps and com Salt, such as, for example, sodium carbonate binations of steps constituting the process or Sodium Sulphate, in order to precipitate and in the novel commercial product result any soluble lime compounds present. This O ing from said process, all as will be more Solution may be made by mixing the crude fully hereinafter disclosed and particularly cyanide with a suitable amount of the sodium pointed out in the claims. salt and treating the mixture with water, or in order that the precise invention may be the crude cyanide and the sodium salt may clearly understood, it is said: In the U. S. be added separately to the water. After so 5 Patent #1,359,257 for cyanide compound lution and precipitation is complete, I filter and process of producing the same, to Wal off the insoluble matter and the precipitated ter S. Landis, and dated November 16, 1920, lime salts, leaving a solution consisting es there is disclosed a process of producing from sentially of Sodium cyanide and sodium commercial cyanamide a crude cyanide of chloride. 20 calcium admixed with other impurities. If this solution should not contain a maxi 70 The process consists essentially in making mum concentration of cyanide and chloride a mixture of crude calcium cyanamide with salts, I remove water by evaporation. pref a flux, such as sodium chloride, the amount of erably under a vacuum, until I obtain a so flux being considerably less than the amount lution Saturated with sodium cyanide. This 25 (of calcium cyanamide present, and heating evaporation is preferably so conducted that 5 the mixture to the fusing point. It is then one obtains from the evaporator a solution quickly cooled to a temperature below 400°C., that is saturated at 34.7°C. or approximately giving a flaky product containing a large at 35° C. with sodium cyanide, and contain amount of calcium cyanide, a smaller amount ing such quantities of soduim chloride as 30 of soduim chloride, and minor amounts of will not crystallize out upon the subsequent lime, graphite and other impurities. When treatment about to be described. this product is dissolved in water there is ob I now take the solution from the evaporator tained a solution of the chlorides and cyanides and cool the same. Crystals of sodium of sodium and calcium together with very cyanide dihydrate (NaCN.2HO) separate 35 small amounts of soluble impurities. This out as the solution is cooled, whereas the com. flaky product is used in the industries in place mon salt stays behind in solution. of sodium cyanide, for example, in the ex If the original solution contains less so traction of the precious metals from their dium chloride than is capable of being main ores, for the production of hydrocyanic acid, tained in solution at the coldest temperature simple and complex cyanides and other com at which the operation is carried out, I may pounds, as an insecticide, and for other uses. add sufficient sodium chloride to the orig On account of the peculiar nature of the inal solution to bring the concentration up to calcium cyanide contained in said crude such point that sodium chloride crystals will cyanide and the influence of the other con not separate out. By this means I may pro 45 stituents, many of which are insoluble, this vide a maximum saturation of the solution patented product has not found application with sodium chloride, in order that the solu in certain industries which require a com tion pressures may cause the crystallization partively pure alkali metal cyanide, and it of a maximum quantity of sodium cyanide is the object of this invention to produce a dihydrate. 50 product from this crude cyanide as a raw ma By carrying out the process in the manner 100 2 1784,562 disclosed, involving the evaporation of a crystallizing out the sodium cyanide dihy solution of sodium cyanide and sodium chlo drate present; and recovering the crystallized ride to such concentration that the resulting hydrated sodium cyanide; and producing solution is just saturated with sodium cyanide from the latter anhydrous sodium cyanide; dihydrate at the transition temperature of substantially as described. 34.7° C. and is just saturated with sodium 2. A process of producing a sodium cya 7 chloride at a temperature just below the low nide from a crude cyanide compound de est point to which I subsequently cool the so rived from crude calcium cyanamide and lution, one is enabled to crystallize out hy containing a substantial percentage of sodium O drated crystals of sodium cyaide substantial chloride consisting in preparing a solution ly uncontaminated with sodium chloride, and of the crude cyanide in water; precipitating therefore have left a mother liquor contain any calcium present; filtering the solution to ing practically no sodium cyanide. In other remove insoluble compounds present; concen words, I thus obtain a substantially com trating the solution; cooling the concentrated 5 plete separation of the two constituents. solution to separate sodium cyanide dihy 8. then separate the crystals from the mother drate; and recovering said sodium cyanide liquor by the usual methods, preferably by from said dihydrate, substantially as de a centrifuge. scribed. I next take the crystals of hydrated so 3. A process of producing sodium cyanide 20 dium cyanide and transfer them into a vac from a crude cyanide compound derived from uum dryer where they melt in their water of crude calcium cyanamide and containing a crystallization, which latter I evaporate off substantial percentage of sodium chloride and obtain a dry sodium cyanide of high consisting in dissolving the crude cyanide in purity as the end product. I treat this said water; adding thereto a soluble salt of sodi product in any desired or usual manner to um capable of precipitating the soluble cal prepare it for the market. I may either cium compounds present; removing the in briquette it or fuse it. soluble compounds present; concentrating the As an example of carrying out this proc solution at a temperature above 35° C.; cool ess, I may take 100 pounds of the crude pat ing the concentrated solution to a tempera 30 ented cyanide carrying approximately 47 ture sufficiently low to cause a separation pounds of calcium cyanide. I mix this with of a substantial portion of the sodium cya approximately 60 pounds of soda ash and dis nide dihydrate present, and recovering sodi solve the same in about 250 pounds of wa um cyanide from the latter, substantially as ter. This gives a solution containing about described. 35 15 per cent of sodium cyanide and 10 to 12 4. A process of producing sodium cyanide per cent of sodium chloride. I concentrate from a crude cyanide compound derived from this solution until the cyanide content is crude calcium cyanamide consisting in dis raised to approximately 20 per cent when it solving the crude cyanide in water; adding will then also contain about 20 per cent of to the solution sufficient sodium chloride to 40 Sodium cyanide and 16 per cent of sodium provide a substantially saturated solution chloride. I now cool the concentrated solu thereof at the lowest temperature of the subse tion down to about minus 15° C. which prac quent operations; adding to the solution a tically separates out all of the sodium cyanide soluble salt of sodium capable of precipitat present in the form of hydrated crystals, as ing any soluble calcium compounds present; 45 above described. removing any insoluble compounds present; I next centrifuge these crystals as dry as concentrating the resulting solution at a tem possible and send the same to a vacuum dryer perature above 35° C.; cooling the concen where I remove the water of crystallization trated solution to a temperature substantial by evaporation, and obtain a final product ly lower than 35°C. to separate out the sodi analyzing about 85 to 90 per cent of pure an um cyanide dihydrate present; and recover hydrous sodium cyanide. ing and drying the latter, substantially as It is evident that those skilled in the art described. may vary the foregoing procedure without 5. A process of producing sodium cyanide departing from the spirit of the invention from a crude cyanide compound derived from 55 and I therefore do not wish to be limited to crude cyanamide consisting in dissolving the the above disclosure except as may be required same in water; adding to the solution a sodi by the claims. um salt capable of precipitating any soluble What I claim is: calcium compound present; filtering off the 1. The process of producing sodium cya precipitated and insoluble compounds in the 60 nide from a crude cyanide compound con solution; adding sodium chloride to the solu taining calcium cyanide and a substantial tion; concentrating the resulting solution; percentage of sodium chloride, which consists cooling the concentrated solution to sepa in preparing from said compound a solution rate out the sodium cyanide dihydrate pres containing essentially sodium cyanide and ent; and drying the latter under a reduced Sodium chloride; concentrating said solution; pressure, substantially as described. l 1,784,562 6. A process of producing sodium cyanide from a crude calcium cyanide containing a substantial percentage of sodium chloride which consists in dissolving the crude cya nide in water, precipitating and removing the calcium, concentrating the solution until the concentration of sodium cyanide dihydrate therein is equivalent to approximate satura tion at 35° C. and cooling the same to a 0. temperature at which the sodium cyanide will precipitate while leaving the sodium chloride in solution. * In testimony whereof I affix my signature. KENNETH F. COOPER. 15

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