V. HYDROMETEES. 143 



651a. A Tan Tester, for ascertaining the exact quantity of 

 tannic acid in any substance by passing it through a piece of hide. 



Thomas Christy and Co. 



The solution having been gauged by a tannometer before being tested and 

 after it has passed through the hide, the difference gives the exact value of any 

 taunic matter, and a merchant knowing the price of oak bark can calculate 

 the value at once of the substance he has tested. 



652. A Salinometer, used on steam vessels to ascertain the 

 amount of salt in the water in the boiler. Dring and Page. 



On the stem of the instrument are the words " limit " and " blow." " Limit " 

 indicates the maximum amount of salt in the water that can be used with 

 safety, and " blow " when it is necessary to blow off a portion of the water in 

 the boiler through there being too much salt in solution. 



653. An Atkins 9 Saccharometer. (Obsolete.) 



Dring and Page. 



654. A Four-weight Hydrometer on Sykes's principle. 

 (Now disused.) Dring and Page. 



The stem is divided into 20 parts, and a part again divided into 2 parts, 

 each of which is equal to one-half per cent. The sliding rule accompanying 

 this instrument gives the equivalents of other hydrometers of the same 

 period. About 1817. 



656. Sykes's (Revenue) Hydrometer. For ascertaining 

 the proof-strength of spirits. Dring and Fage. 



The instrument, used by the Revenue for collecting the duty on spirits, was 

 first established by Act of Parliament in the year 1816 ; by this Act also proof 

 spirit (which forms the basis of estimation in this instrument, as all strengths 

 are indicated by their relation to this point) received a particular definition as 

 that which weighed twelve-thirteenths of an equal bulk of distilled water at a 

 temperature of 51 Fht. The stem of the instrument is divided into 10 parts, 

 and each part again divided into divisions, which, with the nine weights (each 

 of which is a multiple of the divisions of the stem), enables the instrument 

 to measure all gravities from 67 over proof to just past distilled water at 

 60 Fht. The tables which accompany this instrument were compiled from 

 the experiments of Gilpin, who carried them out with such accuracy that no 

 error has ever been detected. The range of temperature given is from 30 to 

 80 Fht. These tables having been found inconvenient for use in hot climates 

 in the year 1851, Messrs. Dring and Fage compiled an extension from 80 to 

 100, which meets all requirements for high temperatures. 



657. Clark's Export Hydrometer (obsolete). Used for 

 ascertaining the strength of spirits in the various stages of manu- 

 facture. Dring and Fage. 



The instrument used for determining the strength of spirituous liquors prior 

 to the introduction of Sykes's hydrometer. This instrument was the first of its 

 kind established by Act of Parliament, and to which any definite kind of cor- 

 rection for temperature was applied. It is constructed to show the number of 

 gallons of water, plus or minus, necessary to reduce to proof strength a sample 

 of spirits under trial, and was only used for spirits in the various stages of 

 manufacture. 



