environment, water and soil, thus are harmful for health (Yang, 2010; USEPA, 2011).

Methyl orange is an azo dye, as it gives sharper end points. In acidic medium it is reddish while in alkali medium it turns yellow. According to Kulkarni, (1985) and Zollinger, (1987) azo dyes are released by many industries such as paper, plastic, leather, food, cosmetics and pharmaceutical industries. Yang, (2010) reported significant environmen- tal pollution from these effluents. Chung et al., (1992) and Kusic et al., (2006) have reported that azo dyes and their degradation products are recognized as potential carcino- gens. As per Santa Cruz Biotechnology Methyl orange may cause eye and skin irritation. If swallowed it may cause gastrointestinal irritation with nausea and vomiting. It may cause respiratory tract irritation.

According to Hassen et al., (2013) the photo degradation of aqueous solution containing azo dye methyl orange decreases the chemical oxygen demand (COD) and total organic carbon (TOC). The toxicity of soil wetted with methyl oranges solu- tion was tested on earthworm (Eisenia andrei) High sensitivity was observed.Merzouk et al., (2009) reported that waste water generated by textile industries contain large amounts of toxic aromatic compounds especially azo dyes. Md. Ali et al., (2011) estimated that 10 to 15 % of the overall production of dyes is released into the environment mainly via waste water It has been reported that the discharge of very small amount of dyes (less than 1 ppm.) is aesthetically displeasing, impedes light penetration, affects gas solubility and may be toxic to treat- ment processes, food chain organisms and aquatic life.

Phenolphthalein is also used as internal indicator in acid base titration. AHFS (1995) reported that the main target organ for the toxic effects of phenolphthalein is intestine which causes chronic ulcerative colitis and involves thinning of intestinal wall and loss of normal mucosal pattern of ter- minal ileum. Nishikawa, (1981) reported that phenolphthalein at doses of 25 to 50 Ug/ml was cytotoxic in cultured liver cells causing decreased cell growth and increased anaerobic glyolysis.

Tice et al., (1998) studied the effects of phenolphthalein at various concentrations in the diet of transgenic female mice for p53 gene, over a six month period. They found signifi- cant increase in the frequency of micro nucleated erythrocytes; these were observed at doses comparable to those to which humans are exposed. According to Sarco, (2010) over dose of phenolpht-halein have been associated with abdominal pain, diarrhoea, vomiting, electrolyte imbalance, dehydration, mal- absorption, weight loss, muscle weakness and prostration. Studies have shown that it is carcinogenic in mice at high dose level and has a weak genotoxic activity in vivo.

Phenol red is also used in acid-base titration. It changes colour from yellow to red over pH range 6.8 (yellow) to 8.2 (red). Above pH 8.2 turns bright pink colour. Phenol red is phenolsulphonphthalein (PSP). It is a weak acid having phe- nolic and sulphonic groups. Warner et al., (1985) reported that phenol red may cause harmful effect on the central nervous system and heart resulting in disrhythmias, seizures and coma. Budavari, (1996) reported that compounds containing phenolic group can cause eye irritation, inflammation of skin, respira- tory irritation which can cause further lung damage.

Jain et al.

Green Chemistry is the solution to these problems. Accord- ing to the United State Environmental Protection Agency, (2011) it is also called as sustainable chemistry is a philoso- phy of chemical research and engineering that encourages the design of chemical products and processes minimizing the use and generation of hazardous waste substances. The principles underlying Green Chemistry also emphasize on the use of sub- stances that possess little or no toxicity to human health and environment.

Flower petals are the substitute for such hazardous inter- nal indicators. Flowers are the miracle of the nature, by God, for the world. Anthocyanins are notable plant pigments which are responsible for red violet blue colour seen in petals (Har- borne, 1998). According to Vanker, (2008) the appearance of red colour is due to the presence of flavonoids, phenols and anthocyanins. Latter may serve as pH indicator in acid base titration. According to Jain et al., (2012) petal extract acts as an indicator in acidimetry and alkalimetry.

Singh et al., (2010) used Nerium oleander, Tecoma stans,

tigated the indicator activity of methanolic activity of Punica granatum. Jain et al. (2012) have used aqueous extract and methanolic extract of Dahlia pinnata and Hibiscus rosa sinen- sis petal extract as acid base indicators.

In the present study Delonix regia (Boj. Ex. Hook.) petal extract was selected as natural indicator for acid base titra- tion. It is commonly known as Gulmohar and in English it is given the name oyal Poinciana or Flamboyant. This tree is commonly cultivated in tropics and subtropics including Madagascar. It belongs to family Fabaceae sub family Cae- salpinioidea. It is grown as an ornamental tree and is noted for its fern like leaves and flamboyant display of flowers. Delonix regia is also having economic importance. Shewale et al., (2012) studied the inflammatory activity of the plant. Parekh et al., (2005) studied the antibacterial activity of aqueous and methanolic extract of Delonix regia. Rajababu et al., (2011) observed antidiarrhoeal activity of Delonix regia in Wistar albino rats.

MATERIAL AND METHODS

Delonix regia was collected was collected for the purpose of study of natural indicator. It was identified from the flora of Botany Department of M. J. Government Girls P.G. College, Indore. Flowers were collected during April to June as it is the blooming season of this plant. The flowers possess four scarlet or orange red spoon shaped petals and a fifth upright petal called the ’standard’ which is slightly larger and spotted with yellow or white.

The spoon shaped petals were plucked from the flower. The standard petal was left away. The petals were cleaned with distilled water and were kept in strong sunlight until they get completely withered. The petals were grinded into fine powder with a mechanical blender. The dried petals were soaked in two beakers one containing 40 ml methanol while the other having 40 ml distilled water for 48 hours