Novriyanti Lubis, ST., M.Si Dosen Pembimbing 1 Riska Prasetiawati, M.Si., Apt. Dosen Pembimbing 1 NISYE NADIA NURARSABAYA Dosen Pembimbing 1

Calcium, an alkaline earth metal, is a major mineral. Calcium is used in the formation of bones and teeth. Various foods are particularly rich in calcium, among others : milk, cheese, and soymilk. soymilk is a good source of calcium, because contains calcium in the proccess of to coagulation protein in soymilk production. Several analytical methods had been reported for calcium assay, including gravimetry, titrimetry, colorimetry, and atomic absorption spectrophotometry. The atomic absorption spectrophotometry is recommended as a method of choice, but it requires an set of expensive instrument. This research was aimed to develop an analytical method of colorimetry using cresolpthalein complexone for determination of calcium. Cresolpthalein complexone would bind the calcium in an alkaline medium to form a purple complex Lich absorbs visible radiation with maximum absorbance at 573 nm. The intensity of the color is propotional to the calcium concentration. The validation of the method was carried out using calcium carbonat. rnThis method is validationed by using calcium salt that is calcium carbonate. The determination of Calcium conducted by simulation of soya milk, the soya milk by adding various of concentration of calcium carbonate and trade of soya milk. The result of Validation method shows that the Relation of concentration calcium carbonate and absorption in the form of straight line with the equation y = 0,006 + 0,344 with the coefficient of correlation 0,997. The limit of detect and each of quantization is 0,017 ppm and 0,056 ppm. Calcium stipulating at sampel of soya milk with the addition of calcium carbonate 200 mg got by a provision value return 83 % with the variation of coefficient ( Vxo) 3.31%, sampel of soya milk by adding calcium carbonate 400 mg got by a provision value return 73,8 % with the variation of coefficient ( Vxo) 0,53% and sampel of soya milk with the addition of calcium carbonate 600 mg got by a provision value return 78,2 % with the variation of coefficient ( Vxo) 0,61%. It can be concluded that the method of analyse colorime by using the complex kresolftalein to analyse the calcium of soya milk, it has carefulness so that it can be used for determination applicable in commerce of soya milk. From the result of the research toward the sampel of simulation of soya milk got mean and calcium in soya milk 52,96 mg / 100 mL The soya milk and sampel trade of soya milk got by mean of calcium rate as 457,9 mg / 100mL of soya milk. rnKeyword : calcium, soya milk, cresoftalein, complexone