Pharaoh’s serpent

Pellets of the dry powder, when ignited in air, form snakelike tubes of spongy ash of unknown composition — the so-called Pharaoh s serpents . 

Pharaoschlange, /. Pharaoh s serpent. Pharmako-log, m. pharmacologist, -logie, /. pharmacology,... 

Mercury (Mercuric) Sulfocyanate (Mercuric thiocyanate, Mercuric rhodamide). Hg(SCN)2, mw 316.77, white powd mp (decompn), poisonous si sol in w (0.07g/100g at 25°), sol in ale and in NH3 NH4 salts. Can be prepd by pptn of Hg nitrate with Amm sulfocyanate and subsequent soln in a large quant of hot w, followed by crystn. Used in prepn of Pharaoh s Serpent and other fireworks (Ref 4)... 

It is a moderately endothermic and thermally unstable compound of high MW (AHy (s) +200.8 kJ/mol, 0.63 kJ/g). A large batch of the damp salt became overheated in a faulty steam drying oven, and decomposed vigorously, producing an enormous Pharaoh s serpent . 

Drying, usually by physical methods, is one of the most common unit operations in both laboratory or industrial scale process chemistry, and since heating is usually employed to remove volatiles, thermally unstable materials may decompose if overheated. As a light-hearted example, when a faulty oven thermostat led to overheating of mercuric thiocyanate, a monstrous Pharaoh s serpent resulted. Drying moist cadmium propionate in an electric oven led to explosive ignition of the diethyl ketone vapour produced as an unforeseen by-product. Drying 3,5-dinitro-2-toluamide had more serious consequences. 

Mercuric thiocyanate, which is formed as a white precipitate when mercuric nitrate and potassium thiocyanate solutions are mixed, is soluble in excess of either solution. When dried, this salt is inflammable, forming a voluminous ash known as Pharaoh s serpents. By the interaction of a mercuric salt with ammonium thiocyanate and thio-carbamide in acetic acid solution in the presence of an oxidising agent, or by the action of hydrogen sulphide on mercuric thiocyanate, the phototropic compound HS.Hg.CNS is obtained.6... 

In practice, more flame is desired than ammonium dichromate alone will give. Weingart34 recommends a mixture of 2 parts of ammonium dichromate with 1 of potassium nitrate and 1 of dextrin. Tinfoil cones are made from circles of tinfoil shaped on a former, and are introduced by means of the former into conical cavities in a block of wood they are then about half filled with the powdered mixture, a Pharaoh s serpent s egg is pressed in, and the edges of the tinfoil are turned down upon it to form the base of the cone. 

Mercuric sulphocyanate has a peculiar property when ignited it burns with the production of a very voluminous coherent ash, which, from the form it assumes, is called Pharaoh s Serpent. It should not be burned indoors because of the production of poisonous vapors. 

The dried salt may be made into the so-called Pharaoh s serpent eggs by mixing it with 1.5 grams of dextrine and water to obtain a paste, placing the latter in conical molds about 1 cm. wide and 1 cm. deep, and letting it dry out and harden. 

Similar to the halides is the thiocyanate, Hg(SCN)2. This compound is also very slightly dissociated, and, consequently, mercuric ions in solution may be titrated with a standard solution of sodium thiocyanate, using a bit of ferric salt as an indicator the end point is marked by appearance of the blood-red color of the FeSCN2+ ion. Students enjoy this titration, not only because the end point is sharp, but also because the solid Hg(SCN)2 so formed may be filtered off, dried, and ignited, whereupon it evolves a voluminous, serpentlike ash (Pharaoh s serpents). 

This compound undergoes rearrangement the same as ammonium cyanate and thio-urea is obtained. With a soluble mercuric salt ammonium thiocyanate precipitates mercuric thio-cyanate which on heating swells up into phantastic shapes which are known as Pharaoh s serpents. The alkyl thio-cyanates are known and have been discussed (p. 74). Allyl-thio-cyanate is a constituent of oil of garlic. These... 

According to Weingart and Lancaster it is important to obtain a good pitch as the raw material e.g. the residue from the distillation of p-naphthol, but the author does not find it easy to get this material at present. In Japan ordinary coal pitch is used but it has a defect for it produces much soot and smoke. There is another kind of snake named Pharaoh s Serpent. The composition contains a mercury compound and may be poisonous. 

Pharaoh s Serpents, This curious chemical toy is prepared as follows l)issolve mercury, with the aid of heat, in dilute nitric acid, being careful that there shall always be an exccvss of mercury present. When the action of the acid has ceased, decant the solution, and pour into it a solution of suipho-cyaiude of potassium or ammonium, which may be procured at any druggist s. Use about equal quantities of the two solutions. A precipitate of sulpho-cyanide of mercury falls out,... 

Many have assumed that the conjurations of the Ancient Egyptians in the time of Moses were produced by some chemical preparation of like nature. Pharaoh s serpents (see Fig 6), are composed of sulpho-cyanide of mercury, which is generally rolled up in a cone of tinfoil and which being lighted at its apex, there issues forth slowly a serpent-like coil, which... 

Ferric thiocyanate, Fe(CNS)3, has a characteristic blood-red color it is formed when a soluble thiocyanate is added to a ferric salt. The reactiton furnishes a convenient test for ferr salts or a thiocyanae. The so-called Pharaoh s serpents are made from mercuric thiocyanate. Ammonium thiocyanate, NH4CNS, is converted by heat into thiourea, SC(NH2)2, the reactions of which are analogous to those of urea, CO(NH2)2. 

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