Abstract: The present invention is one that makes it possible to continuously measure the resistivity of a liquid sample with accuracy as well as preventing the deterioration of the liquid sample associated with measurement, such as change in quality, and relates to a resistivity-measuring circuit C that measures the resistivity in order to sense the deterioration of the liquid sample. The resistivity-measuring circuit C is one that calculates the resistivity of the liquid sample by detecting voltage generated between an outer electrode and an inner electrode, and between the outer electrode and the inner electrode, applies square wave AC voltage having an amplitude of 1 V to 42 V and a frequency of 0.5 Hz to 30 Hz.

Abstract: A lubricant composition for a machining tool, containing: a lubricating base oil; and based on a total amount of the composition, 0.05 to 5% by mass of a phosphoric acid ester represented by (R1O)3P?O: wherein R1 represents any of an aryl group having 6 to 15 carbon atoms and a saturated hydrocarbon group having 1 to 20 carbon atoms, and each R1 may be the same or different; 0.01 to 2% by mass of an acidic phosphoric acid ester represented by (R2O)nP(?O)(OH)(3-n): wherein R2 represents an alkyl group having 4 to 20 carbon atoms, n represents 1 or 2, and R2 may be the same or different; and 0.5% by mass to 5% by mass of a sulfur compound.

Abstract: The present invention provides a compressor oil comprising a hydrocarbon oil having the sulfur content of 0.1% or less by mass and the aromatic content of 1% or less by mass, wherein the content of hydrocarbons having 10 or less carbon atoms is 100 ppm or less by mass based on the total amount of the compressor oil.

Abstract: The present invention is one that makes it possible to continuously measure the resistivity of a liquid sample with accuracy as well as preventing the deterioration of the liquid sample associated with measurement, such as change in quality, and relates to a resistivity-measuring circuit C that measures the resistivity in order to sense the deterioration of the liquid sample. The resistivity-measuring circuit C is one that calculates the resistivity of the liquid sample by detecting voltage generated between an outer electrode and an inner electrode, and between the outer electrode and the inner electrode, applies square wave AC voltage having an amplitude of 1 V to 42 V and a frequency of 0.5 Hz to 30 Hz.

Abstract: A lubricant composition for a machining tool, containing: a lubricating base oil; and based on a total amount of the composition, 0.05 to 5% by mass of a phosphoric acid ester represented by (R1O)3P?O: wherein R1 represents any of an aryl group having 6 to 15 carbon atoms and a saturated hydrocarbon group having 1 to 20 carbon atoms, and each R1 may be the same or different; 0.01 to 2% by mass of an acidic phosphoric acid ester represented by (R2O)nP(?O)(OH)(3-n): wherein R2 represents an alkyl group having 4 to 20 carbon atoms, n represents 1 or 2, and R2 may be the same or different; and 0.5% by mass to 5% by mass of a sulfur compound.