REAGENT TEST FOR DETERMINING THE WATER CONTENT OF A PRODUCT

Abstract: A reagent test for determining the water content of a solid, pulverulent, or liquid product. The reagent test includes a first component comprising water-soluble starch, and a second component comprising iodine in solid form or waterfree solution.

Description: 1 REAGENT TEST FOR DETERMINING THE WATER CONTENT OF A PRODUCT The invention relates to a reagent test for determining the water content of a solid, pulverulent, or liquid product. The invention has been arrived at in connection with determining the water content of toluene which is recovered in printing offices. Toluene-is used as a solvent for printing ink which is delivered in a viscous condition to be diluted later in the printing office to the desired viscosity by the addition of toluene. In the printing machines, toluene is evaporating, b.ut it is not permitted to discharge the evaporating toluene into the atmosphere in view of the environment protection; the evaporated toluene is taken care of in a recovering system. In this system, the evaporated toluene is condensed, the condensate obtained containing some impurities such as oil , metal particles, and water. The major part of these impurities is removed in filters and water separators, but as far as the water content is concerned the purification ' can be carried on to such extent only that tne remaining water content of the toluene is in the range from 0.005 % to 0.05 % . Due to the existing water content the toluene is not chemically pure; it is considered a second class product. Neverthe¬ less sucn toluene is v e ry coveted by the ink industry due to the low price thereof. However, different customers raise different demands on the purity of the toluene and, therefore, it is desired to be able to demonstrate in a simple manner how large the water content is . Methods are already known for demonstrating the water content of toluene, and the most common and known method is the reagent test method according to Karl Fischer. However, this method must be practised in a " laboratory, which is a clear drawback, because specific equipment is required, and the method is time-consuming and expensive. The primary purpose of the invention is to make possible that the water content of toluene is determined in a simple manner which does not require the access to a laboratory but can be practised at the place where the toluene is available, but it has been found that this purpose can be realized also with regard to other liquids as well as solid and pulverulent products. In order to realize said purpose the invention provides a reagent test for determining the water content of a solid, pul verul ent, or liquid product, which is characterized by a first component comprising water-soluble starch, and a second component comprising iodine in solid form or waterfree solution, the presence of water in the product being indicated by blue colour¬ ing of the reagent test when contacted with the product. The invention will be explained in more detail below applied to practical examples. The reagent test of the invention includes two components one of which comprises water-soluble starch which can be in a dry condition, and the other one comprises iodine which can be in solid form or can comprise an alcohol solution such as an ethanol solution containing about 15 % iodine. Preferably, equal amounts by weight of the two components are used. When the reagent test is used for determining the water content of toluene, aoout 15 ml of the toluene is poured into a test glass, the two components of the reagent test then being added. The test glass then is shaken until the reagent test has been solved in the toluene. If water is present in the toluene, there is obtained a blue-coloured precipitation due to the fact that the iodine ions are oxidated to iodine according to the relation J~? J 2 + 2e " The amount of precip tation will be larger the more water present in the toluene. Other aromatic solvents which can be investigated as to the existing water content in the same manner as toluene, are e.g. aircraft fuel , gazoline, heavy oil , fuel oil , benzene, and xylene. .A1so other organic solvents such as chloroform can be investigated as to 10 the existing water content by using the reagent test of the invention. The tests are easily practised at any place, and the reagent test reacts to the existing water content at high sensitivity. E.g. Water contents ranging from 0.005 * to 0.05 % of toluene can be 15 demonstrated . The reagent test is also suitable for a first test analysis of sugar products, grain products, flour products, paper and cellulose in order to determine the water contents thereof. Thus, it has proved possible 20 to demonstrate by using the reagent test of the invention a water content of different carbohydrates with an accuracy of 0.1 % to 0.2 % water content. The carbo¬ hydrates which have been investigated are the following: a) monosacchari des : glycose, fructose, galactose, 25 b) disaccharides: saccharose, lactose, maltose, c e 11 o b i o s e , c) polysaccharides : cellulose, starch. When the reagent test has been used with starch, it has in fact been possible to obtain an accuracy of 30. 0.01 %. It has been found that the sensitivity of the re¬ agent test can be increased by the addition of acetic acid. In that case one component of the reagent test comprises a 15 % iodine solution diluted with 100 % 35 acetic acid in the approximate relationship 1 :1. When ' the reagent test is to be used with solid or pulverulent products, an aromatic solvent initially has to be added to the reagent test, and preferably waterfree toluene or p-xylene is used for this purpose. About 5 ml of this solvent is poured into a test glass, starch and iodine solution then being added together with a test substance, e.g. a pulverulent test sub¬ stance. In the same manner as described above the test glass is shaken to dissolve iodine and starch in the solvent, a more or less intense blue colouring being obtained should the test substance added contain more or less water. If a solid test substance is concerned, the solvent with iodine and starch dissolved therein can be poured onto the solid test substance, but it is also possible to cover the solid substance, e.g. a paper sample, with the dry starch and then pour the solvent, i .e. toluene or p-xylene, with iodine dissolved therein, onto the covering starch. Also the water content of different pulverulent or pulverized chemicals or medicines can be determined by using the reagent test of the invention provided that the chemicals or medicines are substantially whi te or uncoloured such that the blue colouring obtained by means of the reagent test can be observed. In order to determine in a simple manner the approximate water content a colour scale can be constructed. For this purpose the reagent test is added to several different samples which al l comprise one and the same test substance, e.g. toluene, but have different known water contents. In the different samples there is obtained a blue colouring of different intensity depending on the existing water content, and by guidance thereof a colour scale can be constructed. A comparison is then made with this colour scale for determining approximately the water content of a test substance having an unknown water content.

Claims: CLAIMS 1. Reagent test for determining the water content of a solid, pulverulent, or liquid product, which is c h a r a c t e r i z e d by a first component compris¬ ing water-soluble starch, and a second component comprising iodine in solid form or waterfree solution, the presence of water in the product being indicated by blue colouring of the reagent test when contacted with the product. 2. Reagent test as claimed in claim 1, c h a r a c t e r i z e d in that the iodine comprises an alcohol solution, e.g. an ethanol solution, contain¬ ing 15 % of iodine . 3. Reagent test as claimed in claim 1, c h a r a c t e r i z e d in that the reagent test comprises substantially equal amounts by weight of the two components . 4. Reagent test as claimed in claim 1, c h a r a c t e r i z e d in that the iodine solution is diluted with acetic acid, preferably in the approximate relationship 1:1. 5. Reagent test as claimed in claim 1, c h a r a c t e r i z e d in that the reagent test is dissolved in a waterfree aromatic solvent, e.g. to! uene or p-x 1 ene . 6. Reagent test as clai ed in clai 5, c h a r a c t e r i z e d in that the solvent is the product to be investigated by means of the reagent test.

Inventors: OLSSON BOZENA, OLSSON, BOZENA
Applicants: OLSSON BOZENA, OLSSON, BOZENA
Application year: 1985
Main classification: G01N31
IPC codes: G01N31