Practica De Colorimetria

INTRODUCTION

In this lab we will analyze the chemical reaction that occurs when we use different substances to create a flame, it is check the colors that acquires our flame to be exposed to substances such as boric acid or phosphorus.

THEORETICAL FRAMEWORK

In 1859 Gustav Kirchhoff (1824-1887) and Robert Wilhelm Bunsen (1811-1899), teacher of physics and chemistry, respectively, at the German University of Heidelberg, conducted experiments that allowed the first to discover the laws of spectral analysis, which establish a relationship between the ability of bodies to emit and absorb energy. These researchers were passed through a prism the light produced in the lab when heated by a flame a platinum wire impregnated with substances such as sulfur, magnesium and sodium. Kirchhoff realized that each element showed bright lines peculiar to their spectrum. Sodium, for example, showed in the yellow part of the spectrum the presence of two intense lines practically next to each other. Also noticed that those lines fell exactly in the same place occupied Fraunhofer D line in the solar spectrum.

To try to explain this Kirchhoff and Bunsen were passed sunlight through sodium vapor, and saw the two bright lines disappear leaving a dark place that was precisely the line D. Through this experience established the correspondence between the sodium lines produced in the laboratory and appeared dark in the solar spectrum. This experiment concluded that in the Sun's atmosphere had sodium. Shortly after Kirchhoff continued these experiments to try to identify other chemical elements in the solar spectrum. Thus, for example, in the laboratory replaced sodium by lithium and obtained a number of different bright lines that could not be matched to any of the dark lines of the spectrum known as the Sun, from which he inferred that he had not lithium, or if any, will be very little. Following the same procedure established that hydrogen, magnesium, calcium, copper, iron and zinc were present in our star.

Thus each element and its ions when heated to the flame of a Bunsen emit light in the visible region of the electromagnetic spectrum. These colors we serve as "fingerprints" and to identify the different elements containing a sample, but only trace amounts of them.

Premixed flames

There are three different areas:

1. preheating zone: Leaving the fuel / oxidizer has yet to react temperature, increasing as it approaches this next área

2. Reaction Zone: After reaching the ignition temperature of the mixture reacts by releasing heat and forming products based reagents.

3. post reaction zone: The reaction product gases are cooling and stop emitting light.

Diffusion flames

Due to its complexity, is where most progress has been due to advances in measurement gadgetry and can describe various models.

Model three zones or parts of the flame

The first to publish a scientific study of the flame and its structure was Michael Faraday in 1908 with The Chemical History Of A Candle

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