Apparatus and method for dilution and mixing of liquid samples

An apparatus for automatically diluting an aqueous sample with an aqueous diluent, comprising:

• housing means containing
• sample application site means for receiving a sample;
• measuring chamber means having a first volume;
• receiving chamber means having a second volume, wherein said second volume is greater than said first volume;
• diluent application site means for receiving a diluent;
• first flow means for delivering a sample from said sample application site means to said measuring chamber means by the sum of capillary and gravitational forces upon addition of sample to said sample application site means;
• second flow means for delivering diluent from said diluent application site means to said measuring chamber means by the sum of capillary and gravitational forces upon addition of diluent to said diluent application sit means;
• third flow means for delivering sample and diluent from said measuring chamber means to said receiving chamber means by the sum of capillary and gravitational forces;
• and
• a stop flow junction located in said third flow means and adapted to the surface tension characteristics of the sample so as to provide sufficient back pressure resulting from contact between said sample and wall means of said housing means at said stop flow means to prevent sample from flowing through said stop flow junction in absence of diluent but allowing flow through said stop flow junction when diluent is present in said apparatus along with said sample,
• whereby addition of diluent to said diluent application site means after sample is added to said sample application site means causes hydrostatic pressure at said stop flow junction to exceed said backpressure, whereby said diluent expels sample from said measuring chamber means and causes a fixed ratio of sample to diluent to be delivered to said receiving chamber means.