The nascent hydrogen which unites with the nascent nitrogen during the combustion is also derived from the organic matter which always contains enough carbon to decompose the water formed in order to be oxidized to carbon dioxid. While at first, therefore, during combustion, the hydrogen may unite with the oxygen, it becomes again free by the oxidation of the carbon and in this condition unites with the nascent nitrogen to form ammonia. In addition to carbon dioxid, ammonia, and free hydrogen there may also be found among the products of combustion marsh and olefiant gases and other hydrocarbon compounds which dilute, to a greater or less extent, the ammonia formed and help to carry it out of the combustion tube and into the standard acid. =169. The Official Method.=—_Reagents and Apparatus._—(1) Standard solutions and indicator the same as for the kjeldahl method: (2) Dry granulated soda-lime, fine enough to pass a 2.5 millimeter sieve: (3) Soda-lime, fine enough to pass a 1.25 millimeter sieve.[139] Soda-lime may be easily and cheaply prepared by slaking two and one-half parts of quicklime with a strong solution of one part of commercial caustic soda, care being taken that there is enough water in the solution to slake the lime. The mixture is then dried and heated in an iron pot to incipient fusion, and, when cold, ground and sifted as above. Instead of soda-lime Johnson’s mixture of sodium and calcium carbonate, or slaked lime may be used. Slaked lime may be granulated by mixing it with a little water to form a thick mass, which is dried in the water-oven until hard and brittle. It is then ground and sifted as above. Slaked lime is much easier to work with than soda-lime, and gives excellent results, though it is probable that more of it should be used in proportion to the substance to be analyzed than is the case with soda-lime. (4) Asbestos, which has been ignited and kept in a glass-stoppered bottle. (5) Combustion tubes about forty centimeters long and twelve millimeters internal diameter, drawn out to a closed point at one end. (6) Large-bulbed =U= tubes with glass stop-cock, or Will’s tubes with four bulbs.