A method for manufacturing a glass fine particle deposit includes: emitting a siloxane gas, a carrier gas, and a combustion gas from a burner; setting volume concentration of a supply volume amount of the siloxane gas per unit time with respect to the sum of the supply volume amount of the siloxane gas per unit time and a supply volume amount of the carrier gas per unit time (C1) to 10.6 volume %<C1<20.0 volume %; and setting volume concentration of the supply volume amount of the siloxane gas per unit time with respect to the sum of the supply volume amount of the siloxane gas per unit time, the supply volume amount of the carrier gas per unit time, and a supply volume amount of the seal gas per unit time (C2) to 5.8 volume %<C2<10.0 volume %.

A manufacturing method of a porous glass preform for optical fiber by depositing glass microparticles on a starting member, including supplying a vaporizer with organic silicon compound raw material in a liquid state and a carrier gas; in the vaporizer, mixing and vaporizing the organic silicon compound raw material in a liquid state and the carrier gas to convert the organic silicon compound raw material and the carrier gas into a raw material mixed gas; supplying a burner with the raw material mixed gas and a combustible gas, combusting the raw material mixed gas and the combustible gas in the burner, and ejecting SiO.sub.2 microparticles generated by the combustion from the burner; and depositing the SiO.sub.2 microparticles ejected from the burner on the starting member by repeatedly moving a single body, in which the vaporizer and the burner are synchronized, parallel to the starting member in a longitudinal direction thereof.

A method for cleaning a vaporizer that vaporizes, at normal temperature and pressure, a source material in a liquid state, and supplies the vaporized source material to a reactor through a supply pipe, includes a cleaning step of passing the source material to the vaporizer while maintaining the source material in a liquid state to clean the vaporizer.

Described is a process for the production of synthetic fused silica in which the deposition surface is located for a period of at least 50% of the build-up time of the soot body at a burner distance in which the horizontally integrated luminous intensity of the flame of the burner used in the targetless state is still at least ⅔ of the maximum horizontally integrated luminous intensity of the flame.

Described is a method of producing synthetic fused silica in which the synthetic flame used in the method has a ratio of the Full Width at Half Maximum (FWHM.sub.vert) vertical luminous intensity to the Full Width at Half Maximum (FWHM.sub.hori) horizontal luminous intensity greater than 10 in a targetless state, the luminous intensities being measured in candela/mm.sup.2.

A method and an apparatus for producing a porous glass preform by using organosiloxane raw material is provided. The apparatus for producing the porous glass preform 12 according to the present embodiment is configured to mix organosiloxane in a liquid state being a raw material with a carrier gas in a vaporizer 6, heat this mixture to be vaporized, supply this vapor to a burner 13 as a gas raw material, and produce a porous glass preform by depositing a glass fine particle produced by combusting the gas raw material on a starting material, herein the apparatus for producing a porous glass preform includes a moisture removing apparatus 8 configured to remove moisture in the carrier gas and supply the vaporizer with the carrier gas.

Described is a process for the production of synthetic fused silica in which the feedstock vapor is reacted from an organosilicon starting compound and any combustible burner auxiliary gases at an air number in the burner of less than or equal to 1.00. Furthermore, one embodiment relates to a corresponding apparatus.

Provided is a glass fine particle deposit in which a pH of glass fine particles on a surface of the glass fine particle deposit is 5.5 or more and less than 8.5, in which a color difference ΔE*ab with respect to a white calibration plate when the surface of the glass fine particle deposit is measured by the SCI method using a spectrophotometer is 0.5 or more and less than 5. Provided is a method for manufacturing a glass preform including: manufacturing a transparent glass preform by heating a glass fine particle deposit in which a pH of glass fine particles on a surface of the glass fine particle deposit is 5.5 or more and less than 8.5; and measuring the surface of the deposit by the SCI method using a spectrophotometer and determining whether a color difference ΔE*ab with respect to a white calibration plate is 5 or more.

One aspect relates to a process for the preparation of a quartz glass body. The process includes providing a silicon dioxide granulate I prepared from a pyrogenically produced silicon dioxide powder, treating the silicon dioxide granulate I with a reactant at a temperature in a range from 1000 to 1300° C., and making a glass melt out of the silicon dioxide granulate. A quartz glass body is made out of at least a part of the glass melt. Furthermore, one aspect relates to a quartz glass body obtainable by this process. Furthermore, one aspect relates to a light guide, an illuminant, and a formed body, each of which is obtainable by further processing of the quartz glass body. One aspect additionally relates to a process for the preparation of a silicon dioxide granulate II.

When organic siloxane in a liquid state is used as a raw material for glass particles, the formation of polymerized substances is suppressed when the raw material is vaporized in a vaporizer. In the manufacturing method of porous glass base material according to the present invention, the liquid organic siloxane, which is the raw material, is mixed with a carrier gas in the vaporizer, vaporized by the heat generated from the inner wall of the vaporizer heated by a heater unit, and supplied to the burner as a gas raw material. The porous glass base material is manufactured by depositing the glass particles generated by the combustion of the gas raw material on the starting material. The heating output of the heater unit is controlled so that the maximum temperature of the inner wall of the vaporizer is 230° C. or lower.