Flames coloured

In 1801 the French pyrotechnist Claude-Fortune Ruggieri described the use of metal salts in the production of coloured flames. By the early nineteenth century the firework maker had at his disposal a diverse arsenal of materials, many of which are still in use today. The following substances were documented by Audot and others at around that time ... 

The difficulty in producing a good blue flame stems from several important considerations. Firstly, impurities in the chemicals present in the firework tend to produce yellow flames, which detract from the blue secondly, coloured flames follow similar physico-chemical phenomena but operate in different regions of the spectrum. Consequently the copper salts (that are normally utihsed for the production of blue stars) decompose thermally to produce a variety of emissions that radiate from about 325 to 660 nm i.e. from green, blue and violet to orange-red) simultaneously polluting the pure blue flame which appears in the 400 to 455 nm region. 

A lance is a hrework that is about the size of a small pencil that functions in the manner of a flare (Figure 10.3). Thus, the theory of coloured flame production, as presented in Chapter 8, applies equally to the lance. 

Other coloured flames follow similar physico-chemical phenomena but operate in different regions of the spectrum. Consequently, the maker of the coloured lance has at his disposal copper salts for blue, strontium salts for red, sodium salts for yellow and barium salts for green, as shown in Table 10.2. 

B. E. Douda, Theory of Coloured Flame Production , U.S. Naval Ammunition Depot, RDTN No. 71, 1964. 

LANCE Small, tubular firework designed to emit a coloured flame for about 90 seconds. Used for a visual effect in set-pieces. 

Sir Henry E. Roscoe stated in his Spectrum Analysis So long ago as 1752, Thomas Melvill [or Melville], while experimenting on certain coloured flames, observed the yellow soda flame, although he was unacquainted with its cause (63, 64). 

Previous experience indicates that flame emission is preferable for five or six of the elements. With present detectors, reliable measurements can be obtained as long as the ratio Ae/A-0 is superior to 10-7. Therefore, elements such as the alkaline earths that give coloured flames are easily measured by emission (see Table 14.1). 

Cyanogen evolved, burns with a peach coloured flame—cyanide of Hg or Ag. 

We are of opinion, that many of the nitrates might be advantageously employed in the manufacture of fire works. Some, as nitrate of strontian, communicate a red color to flame, as the flame of alcohol. Nitrate of lime also might be used.. . . Muriate of strontian, mixed with alcohol, or spirit of wine, will give a carmine-red flame. For this experiment, one part of the muriate is added to three or four parts of alcohol. Muriate of lime produces, with alcohol, an orange-coloured flame. Nitrate of copper produces an emerald-green flame. Common salt and nitre, with alcohol, give a yellow flame.14... 

Flame colouration Flame colouration through cobalt glass Inferences... 

During the first half of the 19th century numerous experiments were conducted on flames in which colours were produced by injection of various salts. The observation of these coloured flames through a spectroscope showed an emission spectrum of bright lines on a dark background. 

Pre-clean a platinum or nichrome wire by holding it in the hottest part of the Bunsen flame (just above the central blue cone) until there is no coloured flame from the wire. Cool, then dip the cleaned wire into the moistened solid sample. Place the wire at the edge of the Bunsen flame (Fig. 19.3) and record the colour of the flame from the sample (see Table 19.2). 

The diagram is quite convenient for designing colour flame compositions. For example, when a red colour represented by Pi is mixed with a green the new colour moves along the straight line P -Pilike P The coordinates have the following relations ... 

The flame of an alcohol lamp looks almost colourless. Vhen a length of platinum v/ire which is dipped into a metal salt solutioh is put into the flame, the flame is coloured in the upper part by the wire. The colour is peculiar to the kind of the metal strontium colours the flame red, sodium yellow, barium pale green and copper blue. This is applied to the qualitative analysis of metal ions as the colour flame test. The emission of the coloured light is caused by atomic metal gas or a gas consisting of molecules of metal compound, and the process may be set out as follows ... 

To obtain a coloured flame, we use a colour producing material, which is mixed into the composition. The colour depends upon the cation, metal atoms, in the material, and hardly at all upon the anion, e.g. N03,, ... 

The band CuCl appears in a flame which is rich in chlorine or hydrogen chloride gas, and gives the flame a pretty violet blue colour. For example, a composition of 75% ammonium perchlorate, 15% shellac and 10% Paris green produces such a coloured flame. The band CuCl seems to decompose at high temperatures, and it is difficult to produce blue with this band in the high temperatiire class flames, unless the magnesium content is decreased to about 10%. 

Bonfire smoke is produced under the same principle described for black and white smoke. But the difference is that in the case of the bonfire the particles of smoke only absorb the moisture little and do not always grow to a visible size. The smoke therefore sometimes looks almost violet in the distance. The moisture in the air has a great influence upon the growth of the particles of the A-substance when it is hygroscopic. For example, in dry weather a zinc chloride smoke looks thin. A composition which contain ammonium perchlorate, e.g. a colour flame composition or a rocket propellant, has smoke which is almost invisible in dry weather, but it looks quite dense in wet weather. This is due to HCl in the burning gas. A particle of water mist dissolves 00 times its volume of HCl gas at normal temperature. if there is some water mist in the air, the... 

It is thought that fireworks began with the history of potassium nitrate. It has. been used for compositions which produce fire dust or sparks as well as a white smoke which has been called "Wabi (Japanese fire). It could not produce coloured flames, but before the appearance of potassium chlorate, fireworkers made various efforts to create colour with it as far as possible. 

It is used for coloured flame compositions, but the burning rate is not so great as it is with potassium chlorate compositions. On burning it does not smell of chlorine gas. The available oxygen per 1 gram of potassium perchlorate -amounts to 0. 62grams, which is I.I8 times more than that of potassium chlorate. 

Barium chlorate burns well in combination with shellac in a weight ratio 10 2,producing a beautiful green coloured flame. The spectrum consists of three clear bands of BaCl molecules, thus it has the ability to produce green colour even in low temperature class flames (without magnesium as... 

A white powder. It is known as a chlorine donor for producing coloured flames. It contains 66-67% chlorine and is easily soluble in acetone, but it is insoluble in alcohol(s. Lancaster s book p.3 ) ... 

When BHC is heated, it vaporizes without carbonization. It is difficult to ignite BHC or its vapour in the air, but when once ignited, it burns generating soot and HCl gas. Therefore it is used as an HCl producing agent and reduction agent for coloured flames. But it is not as effective as PVC. But in the case,of twinklers BHC is used for the compositions in place of PVC, because BHC does not disturb the flickering of the flame. 

Prepare a coloured flame composition. Sandwich it with several sheets... 

Three oxidizers, potassium chlorate, potassium perchlorate and ammonium perchlorate, give a quite similar distribution of temperature in combination with shellac along the length of the flame. The maximum temperature is obtained at 75 weight % of the oxidizer without reference to its type, where the ratio F/0, which means the weight ratio of the fuel to the oxidizer, amounts to 17 83 or 20 100.The maximum temperature amounts to more than 2250°C for potassium perchlorate, 2200°C for ammonium perchlorate and 2180°C for potassium chlorate, and these values are not very different from each other. The temperature effect of the three oxidizers is enough to excite emitters so that good coloured flames can be obtained. 

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