BACKGROUND

[0001] Calcium carbonate has an influence on several soil properties such as soil pH, adsorption-desorption and soil cementation. Accordingly it is desirable to test soil samples for calcium carbonate content. Several testing methods exist including calcimetry, ion chromatography and flame emission spectrometry. Advantageously, calcimetry is an inexpensive and straightforward method of analysis. Unfortunately it suffers from a few drawbacks such as a long testing time and interference from environmental conditions.

Accordingly, there is a need for an improved method of calcimetry.

BRIEF DESCRIPTION

[0002] Disclosed herein is a method for determining calcium carbonate levels in soil comprising: reacting a soil sample and hydrochloric acid in a vessel to produce carbon dioxide, wherein the vessel has a single outlet that is in gaseous communication with a measurement device comprising an aqueous measuring liquid and the measurement device is in liquid communication with a reservoir comprising the aqueous measuring liquid and a nonaqueous layer disposed the surface of the aqueous measuring liquid in the reservoir;

determining the displacement of the aqueous measuring liquid by the produced carbon dioxide in the measurement device and comparing the amount of displacement to a calibration curve to determine the amount of carbon dioxide produced; wherein the nonaqueous layer has a density which is less than the density of the aqueous measuring liquid.

[0003] Also disclosed herein is an apparatus for determining calcium carbonate levels in soil. The apparatus comprises: a reaction vessel having a single outlet that is in gaseous communication with a measurement device comprising an aqueous measuring liquid and the measurement device is in liquid communication with a reservoir comprising the aqueous measuring liquid and a non-aqueous layer disposed the surface of the aqueous measuring liquid in the reservoir; and further wherein the non-aqueous layer has a density which is less than the density of the aqueous measuring liquid.

[0004] The above described and other features are exemplified by the following figure and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 shows one embodiment of the apparatus.

DETAILED DESCRIPTION

[0006] A soil sample comprising calcium carbonate placed in contact with a strong acid, such as hydrochloric acid, in a reaction vessel produces carbon dioxide as shown below:

CaC0 ₃ + 2HC1→ CaCl ₂ + H ₂ 0 + C0 ₂ †

[0007] The volume of carbon dioxide produced is proportional to the amount of calcium carbonate present in the soil sample. The reaction vessel is in gaseous

communication with a measurement device. The measurement device comprises an aqueous measuring liquid and markings to determine the displacement of the aqueous measuring liquid. The aqueous measuring liquid is displaced when the carbon dioxide is produced and the quantity of displacement can be compared to a calibration curve to determine the amount of carbonate in the original sample. Currently this technique is performed as described in this paragraph and several problems exist. The aqueous measuring liquid is also exposed to the ambient atmosphere (room air) in the reservoir and the carbon dioxide content in the aqueous measuring liquid can fluctuate. As the carbon dioxide content in the aqueous measuring liquid fluctuates the displacement of the aqueous measuring liquid from sample to sample is inconsistent due to variations in the absorption of carbon dioxide by the aqueous measuring liquid. These variations decrease both the accuracy and the precision of the method. A simple and elegant solution to the problem is a non-aqueous layer used in combination with the aqueous measuring liquid. The non-aqueous layer has a density less than the aqueous measuring liquid ensuring that the non-aqueous layer is between the aqueous measuring liquid and the ambient atmosphere. The non-aqueous layer forms a barrier, limiting the absorption and desorption of carbon dioxide by the aqueous measuring liquid, thus improving both accuracy and precision of the measurement.

[0008] The non-aqueous layer comprises a non-aqueous liquid which has limited miscibility with the aqueous measuring liquid. "Limited miscibility" describes a material which forms a visible layer separate from the aqueous measuring liquid. The non-aqueous layer absorbs little or no carbon dioxide from the atmosphere and is substantially inert to both the aqueous measuring liquid and the ambient atmosphere for greater than a week, or, more specifically, greater than a month, or even more specifically, greater than two months, or, even more specifically, greater than six months. In some embodiments the non-aqueous layer can comprise linseed oil, castor oil, mineral oils, olive oil, vegetables oils, liquid monomers, engine oils, or a combination thereof. In one embodiment the non-aqueous layer consists of linseed oil. In some embodiments the non-aqueous liquid has a density of 0.5 to 0.99 milligrams per cubic centimeter. The viscosity of the non-aqueous liquid can be 40 centipoise (cP) at 25 °C to 1200 centipoise (cP) at 25 °C.

[0009] The non-aqueous layer is used in a quantity sufficient to form a complete layer across the surface of the aqueous measuring liquid. In some embodiments the non-aqueous layer has a thickness of 0.5 to 30.0 millimeters, more specifically, 0.5 to 15.0 millimeters, or, even more specifically, 0.5 to 5.0 millimeters.

[0010] The aqueous measuring liquid can be acidified to minimize any reaction with carbon dioxide and also limit absorption of carbon dioxide by the aqueous measuring liquid. In some embodiments the aqueous measuring liquid has a pH less than or equal to 6, more specifically, a pH of 4 to 6, even more specifically a pH of 5 to 6.

[0011] In an alternate embodiment, the aqueous measuring liquid is saturated with carbon dioxide immediately prior to the application of the non-aqueous layer.

[0012] In some embodiments the aqueous measuring liquid comprises a colorant for better visibility. The colorant can be chosen depending on the pH of the aqueous measuring liquid in order to maximize the stability of the colorant at the pH of the aqueous measuring liquid. Exemplary colorants include inorganic pigments, organic pigments, and dyes. The colorant should be soluble in the aqueous measuring liquid. Suitable colorants can be obtained from, for example, Becker Underwood, Elementis Pigments, Bayer, BASF, and Clariant.

[0013] The aqueous measuring liquid is located in a measurement device. The measurement device may be any shape provided that it comprises a marking system that allows the determination of the displacement of the aqueous measuring liquid (and nonaqueous layer). One exemplary measurement device is a column having markings corresponding to a unit of measurement such as milliliters and the like. The measuring device is in liquid communication with a reservoir. The reservoir comprises the aqueous measuring liquid and the non-aqueous layer disposed on the aqueous measuring liquid.

[0014] The method comprises reacting a soil sample and hydrochloric acid in a reaction vessel to produce carbon dioxide. The reaction vessel has a single outlet that is in gaseous communication with the measurement device. A typical soil sample is O.lto 10 grams and approximately 0.5 to 15.0 milliliters of concentrated (6 Normal) hydrochloric acid (HCl) are used. The soil sample and the HCl are mixed and allowed to react, typically for 0.5 to 5.0 minutes. As the reaction proceeds and produces carbon dioxide the aqueous measuring liquid is displaced in the measurement device. The amount of displacement is determined and compared to a calibration curve.

[0015] The calibration curve is obtained through the reaction of known quantities of calcium carbonate and specified amounts of concentrated HCl. The amount of displacement produced by each known sample is measured and plotted (displacement versus calcium carbonate quantity)

[0016] The method and apparatus may be better understood after reviewing the figures. In Figure 1, the reaction vessel (10) is in gaseous communication with the measurement device (20). The reservoir of the aqueous measuring liquid (30) is in liquid communication with the measurement device. The apparatus is supported by a stand (40).

[0017] Set forth below are examples of the method and apparatus disclosed herein.

[0018] Embodiment 1: A method for determining calcium carbonate levels in soil comprising: reacting a soil sample and hydrochloric acid in a vessel to produce carbon dioxide, wherein the vessel has a single outlet that is in gaseous communication with a measurement device comprising an aqueous measuring liquid, wherein the measurement device is in liquid communication with a reservoir comprising the aqueous measuring liquid, and wherein a non-aqueous layer is disposed on the surface of the aqueous measuring liquid in the reservoir; and determining the displacement of the aqueous measuring liquid by the produced carbon dioxide in the measurement device and comparing the amount of displacement to a calibration curve to determine the amount of carbon dioxide produced; wherein the non-aqueous layer has a density which is less than the density of the aqueous measuring liquid.

[0019] Embodiment 2: The method of Embodiment 1, wherein the non-aqueous layer comprises linseed oil, castor oil, mineral oils, olive oil, vegetables oils, liquid monomers, engine oils, or a combination comprising at least one of the foregoing.

[0020] Embodiment 3: The method of any of Embodiments 1 - 2, wherein the nonaqueous layer consists of linseed oil.

[0021] Embodiment 4: The method of any of Embodiments 1 - 3, wherein the nonaqueous layer has a density of 0.5 to 0.99 milligrams per cubic centimeter. [0022] Embodiment 5: The method of any of Embodiments 1 - 3, wherein the nonaqueous layer has a viscosity of 40 centipoise (cP) at 25 °C to 1200 centipoise (cP) at 25 °C

[0023] Embodiment 6: The method of any of Embodiments 1 - 5, wherein the nonaqueous layer has a thickness of 0.5 to 30.0 millimeters.

[0024] Embodiment 7: The method of any of Embodiments 1 - 6, wherein the nonaqueous layer has a thickness of 0.5 to 5.0 millimeters.

[0025] Embodiment 8: The method of any of Embodiments 1 - 7, wherein the aqueous measuring liquid has a pH less than or equal to 6.

[0026] Embodiment 9: The method of any of Embodiments 1 - 8, wherein the aqueous measuring liquid comprises a colorant.

[0027] Embodiment 10: An apparatus for determining calcium carbonate levels in soil comprising: a vessel having a single outlet that is in gaseous communication with a measurement device comprising an aqueous measuring liquid, wherein the measurement device is in liquid communication with a reservoir comprising the aqueous measuring liquid, and wherein a non-aqueous layer is disposed the surface of the aqueous measuring liquid in the reservoir; and further wherein the non-aqueous layer has a density which is less than the density of the aqueous measuring liquid.

[0028] Embodiment 11: The apparatus of Embodiment 10, wherein the non-aqueous layer comprise linseed oil, castor oil, mineral oils, olive oil, vegetables oils, liquid monomers, engine oils, or a combination comprising at least one of the foregoing.

[0029] Embodiment 12: The apparatus of any of Embodiments 10 - 11, wherein the non-aqueous layer consists of linseed oil.

[0030] Embodiment 13: The apparatus of any of Embodiments 10 - 12, wherein the non-aqueous layer has a density of 0.5 to 0.99 milligrams per cubic centimeter.

[0031] Embodiment 14: The apparatus of any of Embodiments 10 - 13, wherein the non-aqueous layer has a viscosity of 40 centipoise (cP) at 25 °C to 1200 centipoise (cP) at 25 °C.

[0032] Embodiment 15: The apparatus of any of Embodiments 10 - 14, wherein the non-aqueous layer has a thickness of 0.5 to 30.0 millimeters.

[0033] Embodiment 16: The apparatus of any of Embodiments 10 - 15, wherein the non-aqueous layer has a thickness of 0.5 to 5.0 millimeters.

[0034] Embodiment 17: The apparatus of any of Embodiments 10 - 16, wherein the aqueous measuring liquid has a pH less than or equal to 6. [0035] Embodiment 18: The apparatus of any of Embodiments 10 - 17, wherein the aqueous measuring liquid comprises a colorant.

[0036] The method and apparatus are further described in the following non-limiting examples.

EXAMPLES

[0037] The following examples were performed by combining 1.0 grams of a soil sample with 10.0 milliliters of 6N HC1 in a reaction vessel. The reaction vessel was in gaseous communication with a measuring device as described above. After 2.0 minutes the displacement of the aqueous measuring liquid was determined and compared to a calibration curve to determine the amount of calcium carbonate in the soil sample. To compare results across several methods a larger soil sample was divided into smaller portions for testing. In Table 1 below a reference method was compared to a calcimetry as described in the prior art (without a non-aqueous layer) and calcimetry with a non-aqueous layer disposed on the surface of the aqueous measuring liquid in the reservoir in liquid communication with the aqueous measuring liquid in the measuring device. The non-aqueous layer was linseed oil and the layer had a depth of 5.0 mm. All values in bellow table are average of numbers of at least three test results.

[0038] Soil samples tested using a calcimeter having a non-aqueous layer disposed on the surface of the aqueous measuring liquid in the reservoir in liquid communication with the aqueous measuring liquid in the measuring device show excellent agreement with the samples tested by the reference method. The comparative method (tested without the nonaqueous layer) shows poor agreement with the reference method.

[0039] Sample F was tested using other materials as the non-aqueous layer. The nonaqueous layer was allowed to stay in the apparatus for an extended period of time. Sample F was tested when the non-aqueous layer was put in place and then again after a specified period of time. Linseed oil demonstrated the best long term stability. Results are shown in Table 2.

[0040] The data in Table 2 shows that the measurement method has the best long term stability when linseed oil is used as the non-aqueous layer.

[0041] In general, the invention may alternately comprise, consist of, or consist essentially of, any appropriate components herein disclosed. The invention may additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants or species used in the prior art compositions or that are otherwise not necessary to the achievement of the function and/or objectives of the present invention.

[0042] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., ranges of "up to 25 wt.%, or, more specifically, 5 wt.% to 20 wt.%", is inclusive of the endpoints and all intermediate values of the ranges of "5 wt.% to 25 wt.%," etc.). "Combination" is inclusive of blends, mixtures, alloys, reaction products, and the like. Furthermore, the terms "first," "second," and the like, herein do not denote any order, quantity, or importance, but rather are used to denote one element from another. The terms "a" and "an" and "the" herein do not denote a limitation of quantity, and are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The suffix "(s)" as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., the film(s) includes one or more films). Reference throughout the specification to "one embodiment", "another embodiment", "an embodiment", and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments.

[0043] While particular embodiments have been described, alternatives,

modifications, variations, improvements, and substantial equivalents that are or may be presently unforeseen may arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they may be amended are intended to embrace all such alternatives, modifications variations, improvements, and substantial equivalents.

[0044] I/we claim: