[Catasoonat] Ferrocyanide of potassium (K,Fcy + 2 Aq.) Yellow prussiatc of potash.
This salt is prepared by heating together, in a covered iron pot, a mixture of about five parts of horn parings, hide clippings, horse's hoofs or other similar refuse animal matter, with about two parts of pearlash, and a quantity of scrap iron. At the high temperature employed the nitrogen and carbon combine to form cyanogen, and this, with the iron and potassium of the pearlash, forms ferrocyanide of potassium. On digesting the cooled mass in water and evaporating the solution, the salt crystallises out in large yellow crystals derived from the octohedron.
Ferridcyanide of potassium Red prussiate of potash. This salt is formed on passing chlorine through a dilute solution of the ferrocyanide, till the latter ceases to give a blue precipitate with a persalt of iron. On evaporation and recrystallisation magnificent ruby red prisms are obtained. For the relative composition, probable con stitution, and uses of ferrocyanide and ferridcyanide of potassium see CYANOCEN; FERRIDCYANIO ACID; FERROCYA.NIC ACID; METALS, Iron, ferrocyanogen and ferrideyanogen ; BLUE, prussian blue.
Sulphocyanide of potassium. See CYANOOEN. K Potassium-amide (H N) is a primary inorganic monamide, formed H on gently heating potassium in a current of dry ammoniacal gas ; hydrogen is at the same time evolved. It is a fusible, semi-crystalline
olive-green compound. Heated to redness it is decomposed, a greenish black infusible body remaining, which is the corresponding tertiary monamile, or nitride of pcgassimn 1 K N).
!ktefticn of pMessium. The salts of potassium are eharacterised, first, by communicating a purple colour to the blowpipe flame; second, by affording a crystalline precipitate on being mixed with excess of a saturated solution of bitartrate of soda—this test may not succeed if the potassium be present only in small quantity ; third, by giving a yellow granular precipitate on the addition of bichloride of platinum.
Estimation of potassium. This is usually effected in the state of the double chloride of potassium and platinum just mentioned (KCI, PtC1,1. The substance— from which all other metals have been seserated by the ordinary system of analysis—is acidulated with hydrochloric acid, the bichlonde of platinum added, and the whole evaporated to dryness. The residue Is then washed with a mixture of alcohol and ether, and weighed on a tared filter ; 100 parts are equiva lent to 15.PS of potassium, or 19•26 of potash (KO).