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Small hand-cranked tube centrifuges were commonly used on dairy farms in the early 20th century, while larger versions, powered by a steam turbine or belt drive, were used in commercial dairies. Although not yet generating the collector interest shown for the hand cranked cream separators (continuous flow centrifuges), early and rare tube centrifuges are actively sought.
Cream separators were first introduced in Denmark, in 1878, and rapidly spread through Europe and America. While various tests were devised for measuring the fat content of milk in the 1880’s, most were beyond the expertise of the average farmer, who wanted to compare the butter fat content of milk from each of his cows. In 1888, F.C. Short, of the University of Wisconsin, published a paper on a milk test in which the sample was first treated with a strong alkali and then an acid. Separation of the released fat was achieved by gravity, which required the samples to stand in a hot water bath at least 1 hour, and a mathematical formula was required to convert the length of the fat column in the neck of the tube into percent fat. In 1890, a colleague of Short, at Madison, S.M. Babcock, published his famous paper on the “Babcock” milk test. This much simpler test required the addition of sulfuric acid, but, a calibrated test bottle was used so the percent fat could be read directly on the tube. In addition, a small centrifuge was used to greatly hasten and improve the separation. This test proved extremely popular and test kits were heavily marketed to farmers, all including a small hand operated centrifuge.
While it is commonly believed that all such centrifuges must be no earlier than Babcock’s 1890 paper, in fact, the earliest reference I have found to a tube centrifuge for testing the cream content of milk was published in The Cultivator and Country Gentleman, in 1881. The author, Henry Alvord, of Hampshire County, Massachussetts, describes the centrifuge in detail, including its swinging buckets and water cushion tubes. The device was invented by Rev. H.F. Bond, of Worcester County, Mass, and was being manufactured in Northborough. One of the machines, costing $10, had been in use by the city milk inspector of Boston for several months. I have found no record of any advertising for this centrifuge and no patent was granted.
Two milk test centrifuges were patented prior to 1890. The first, filed in 1894, used special narrow neck tubes inserted into horizontal holes drilled in the segmented wooden rotor. The tubes had graduated necks for directly reading the percent fat, with different tubes provided for testing skim milk, buttermilk, or cream. The test did not involve treating the milk with acid. In 1889, a patent was granted for a geared, hand cranked centrifuge for testing milk, along with a gauge for measuring the meniscus in the sample tubes. The milk was untreated and the scale on the gauge was not defined.
Thus, most of the components of the Babcock test were devised and put to use by others prior to Babcock’s 1890 paper. However, his was the first highly accurate and quick assay that did not tax the average farmer’s knowledge of chemisty and mathematics.
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