Group flame tests

Radium, the last element in the group, was isolated in trace amounts as the chloride by P. and M. Curie in 1898 after their historic processing of tonnes of pitchblende. It was named by Mme Curie in allusion to its radioactivity, a word also coined by her (Latin radius, a ray) the element itself was isolated electrolytically via an amalgam by M. Curie and A. Debieme in 1910 and its compounds give a carmine-red flame test. 

Because its outet valence electrons ate at a gteatet distance from its nuclei, potassium is more reactive than sodium or lithium. Even so, potassium and sodium are very similar in their chemical reactions. Due to potassiums high reactivity, it combines with many elements, particularly nonmetals. Like the other alkali metals in group 1, potassium is highly alkaline (caustic) with a relatively high pH value. When given the flame test, it produces a violet color. 

A similar kind of synergy was investigated by Cui et al.,90 who prepared by melt blending nano-modified ATH using oxalic acid, a red phosphorus masterbatch and high impact polystyrene (HIPS). Unfortunately, the use of variable amounts of HIPS in the compositions has limited the possibility to see evidence of synergistic effects. The authors have stressed the well-developed and robust character of the char layer formed after UL-94V flame test for the composition HIPS/modified ATH/ Red phosphorus (68/20/12). The use of FTIR confirmed also that both P-O-P and P-O-C groups were present in the char. 

Group reagent there is no common reagent for the cations of this group. Group reaction cations of the fifth group do not react with hydrochloric acid, hydrogen sulphide, ammonium sulphide or (in the presence of ammonium salts) with ammonium carbonate. Special reactions or flame tests can be used for their identification. 

Because NaOH is added in group 3 and Na2C03 is added in group 4, the flame test for Na ions is carried out using the original solution. 

With the exception of aluminum, which is one of the most abundant elements in Earths crust, most of the boron group elements are rare. None of the elements are found free in nature. Three can be identified by flame tests, as shown in the table. Boron produces a bright green color, while indium produces an indigo blue color. Thallium produces a green color. More precise identification methods involve advanced spectral and imaging techniques. 

Because the group 14 elements bond covalently, they do not lend themselves to identification through flame tests. The exception is lead, which produces a light-blue color. The carbon group elements can be identified through analysis of their physical properties (melting point, boiling point, density), emission spectra, or reactions with other chemicals. For example, tin and lead form precipitates when added to specific solutions. 

Because group 15 elements bond covalently and most are nonmetallic in nature, they do not lend themselves to identification through flame tests. The exceptions are antimony and bismuth. Antimony produces a faint green or blue color when placed in a flame, while bismuth produces a light purple-blue color. 

The different polymers maybe classified into several groups according to the element present as shown in Table 3.9. The focus of identification may be further narrowed down on the basis of other preliminary observations, e.g., fusibifity or otherwise, melting point or range, heat distortion temperature, flame tests... 

During the last years, a number of products consisting of a mixture of different plastics have made their appearance they are usually called polymer blends or polymer alloys. Their identification using simple methods presents considerable difficulties because flame tests and pyrolysis tests are usually not unambiguous. Also a separation into different groups according to the pH-value of the pyrolysates does not permit a definite conclusion. In some cases, however, it is possible to separate polymer mixtures into their components if these have different solubility characteristics and then to identify the components (see Section 6.3). 

Table 11-1 Flame Test Colors of Group 1 Metals...

Group 5. The alkali metal ions and The ions that remain after removing the insoluble phosphates are tested for individually. A flame test can be used to determine the presence of KT, for example, because the flame turns a characteristic violet color if is present. 

Some of the Group 2 metals burn with characteristic flame colours. It is the 2+ ions formed in the reaction that cause the colours. We can test for calcium, strontium and barium in compounds using flame tests. A nichrome wire, cleaned with concentrated hydrochloric acid, is dipped into a sample of the salt to be tested and heated in a non-luminous Bunsen flame ... 

This test method for naphthalene hydrocarbons is one of a group of tests used to assess the combustion characteristics of aviation turbine fuels of the kerosene boiling range. The naphthalene hydrocarbon content is determined because naphthalenes, when burned, tend to have a relatively larger contribution to a sooty flame, smoke, and thermd radiation than single ring aromatics. 

The flash point of a petroleum liquid is the temperature to which it must be brought so that the vapor evolved burns spontaneously in the presence of a flame. For diesel fuel, the test is conducted according to a closed cup technique (NF T 60-103). The French specifications stipulate that the flash point should be between 55°C and 120°C. That constitutes a safety criterion during storage and distribution operations. Moreover, from an official viewpoint, petroleum products are classified in several groups according to their flash points which should never be exceeded. 

All the cations of Group I produce a characteristic colour in a flame (lithium, red sodium, yellow potassium, violet rubidium, dark red caesium, blue). The test may be applied quantitatively by atomising an aqueous solution containing Group I cations into a flame and determining the intensities of emission over the visible spectrum with a spectrophotometer Jlame photometry). 

---