Povidone-iodine is also efficient against fungi and viruses (including HIV and "Herpes simplex"). It is used in pleurodesis (fusion of the pleura because of incessant pleural effusions). For this purpose, povidone-iodine is equally effective and safe as talc, and may be preferred because of easy availability and low cost. There is tentative evidence that chlorhexidine and denatured alcohol used to clean skin prior to surgery is better than povidone-iodine with alcohol; however, the evidence is not strong enough as of 2015 to determine routine practice. PVP-I is contraindicated in patients with hyperthyroidism (overactive thyroid gland) and other diseases of the thyroid,
Iodine and iodate anions are often used for quantitative volumetric analysis, for example in iodometry and the iodine clock reaction (in which iodine also serves as a test for starch, forming a dark blue complex), and aqueous alkaline iodine solution is used in the iodoform test for methyl ketones. The iodine test for starch is still used to detect counterfeit banknotes printed on starch-containing paper. The spectra of the iodine molecule, I, consists of (not exclusively) tens of thousands of sharp spectral lines in the wavelength range 500-700 nm. It is therefore a commonly used wavelength reference (secondary standard). By measuring