Item Description: 3.6ml of 1.81 Refractive Index for Gem Refractometers, American Made, ARSENIC FREE! THE LARGEST SIZE AVAILABLE ANYWHERE! THIS IS THE BEST FLUID AVAILABLE FOR GEM REFRACTOMETERS! This product is the non-poisonous version of the classic Gem Refractive Index Fluid; Diiodomethane (methylene iodide). The most important aspect of the Refractometer is the quality of the fluid and its Refractive Index. This product has a Refractive Index value of 1.81RI and is THE best product for accurate GEM Identification. The 4.0ml vial has an applicator rod inside the cap for easy application and holds 3.6ml of fluid (so the vial ALMOST full!). The big , factory sealed bottle only has 2.5ml (the 10 gram bottle)! This is the BEST deal for the money! The Gem Refractometer Liquid has a refractive index of nD = 1.810, the highest of any liquid not containing arsenic. As the name implies, it is widely used with gem refractometers as a contact medium for the identification of gemstones. This light yellow liquid can also be used to reduce or eliminate glare from a gem's surface, facilitating inspection of the gem's interior for inclusions and other defects. This liquid is supplied by a highly reputable American supplier in bulk and repackaged in an amber glass bottle. The cap has a plastic applicator rod attached to it on the inside, designed to deliver a small droplet. To ensure the liquids maximum shelf life, keep this liquid tightly sealed after opening, store it away from direct light and in moderate temperatures. Specifications: Refractive Index @ 25'C: nD = 1.81 +/- 0.005 @ 25C Appearance and color: Golden Liquid Boiling Point at 760 mm Hg: 181 C (358 F) pH: Not applicable Vapor Pressure: 760 mm Hg @ 23 C/73 F...1.5 Viscosity: Not applicable, but close to an ISO 5 Specific Gravity (water = 1) @ 23 C/73 F: 3.14 Water solubility: Slight Octanol/Water Partition Coefficient in Kow: Specific value not known Melting/Freezing Point: 20C (68f) Evaporation Rate (mineral oil = 1, 760 mm Hg, 73 F/23 C): 1 This product is the non-poisonous version of the classic Gem Refractive Index Fluid; Diiodomethane (methylene iodide). It is not carcinogenic according the the product MSDS. National Industrial Supply 30777 Rancho California #891420 Temecula, CA 92589, USA Sales: 951.308.9269 - Fax: 310.733.5480 - E-mail: nisupply@gmail.com - Website: www.nisupply.com